Remove default configuration from .rubocop.yml

We had part of the default Rubocop configuration in the `.rubocop.yml`
file. It is not needed as it is the default and it also don't make
sense, because we only have part of it.

That was caused because when enabling a cop we were moving it from
`.rubocop_todo.yml` to `.rubocop.yml`, but this is only needed if we
overwrite the default configuration.

.rubocop.yml

@@ -13,112 +13,6 @@ AllCops:
     - 'config/**/*'
     - 'bin/*'
 
-#################### Style ###############################
-
-# Align the elements of a hash literal if they span more than one line
-Style/AlignHash:
-  Enabled: true
-
-# Align the parameters of a method call if they span more than one line
-Style/AlignParameters:
-  Enabled: true
-
-# Use && instead of and, use || instead of or
-Style/AndOr:
-  Enabled: true
-
-# Avoid redundunt curly braces when it is obvious that hash is used
-Style/BracesAroundHashParameters:
-  Enabled: true
-
-# Avoid the use of the case equality operator `===`
-Style/CaseEquality:
-  Enabled: true
-
-# Use nested module/class definitions instead of compact style
-Style/ClassAndModuleChildren:
-  Enabled: true
-
-# Checks the . position in multi-line method calls.
-Style/DotPosition:
-  Enabled: true
-
-# Checks for uses of double negation (!!) to convert something to a boolean value.
-Style/DoubleNegation:
-  Enabled: true
-
-# Use one empty line between method definitions
-Style/EmptyLineBetweenDefs:
-  Enabled: true
-
-# There should be only one empty line in designated place
-Style/EmptyLines:
-  Enabled: true
-
-# Keep a blank line before and after private.
-Style/EmptyLinesAroundAccessModifier:
-  Enabled: true
-
-# Use hash literal {} instead of Hash.new
-Style/EmptyLiteral:
-  Enabled: true
-
-# Prefer `each` over `for i`
-Style/For:
-  Enabled: true
-
-# Use the new Ruby 1.9 hash syntax
-Style/HashSyntax:
-  Enabled: true
-  EnforcedStyle: ruby19
-
-# Checks for uses of if with negated condition. Use unless instead
-Style/NegatedIf:
-  Enabled: true
-
-# Do not compare with nil. Use .nil? instead
-Style/NilComparison:
-  Enabled: true
-
-# Checks for redundant uses of self.
-Style/RedundantSelf:
-  Enabled: true
-
-# Checks that operators have space around them, except for ** which should not have surrounding space.
-Style/SpaceAroundOperators:
-  Enabled: true
-
-# Checks for spaces inside square brackets.
-Style/SpaceInsideBrackets:
-  Enabled: true
-
-# This cop enforces the use the shorthand for self-assignment.
-Style/SelfAssignment:
-  Enabled: true
-  
-# Use single quotes unless there's string interpolation
-Style/StringLiterals:
-  Enabled: true
-
-# This cop checks for tabs where spaces should be used.
-Style/Tab:
-  Enabled: true
-
-# Avoid trailing blank lines
-Style/TrailingBlankLines:
-  Enabled: true
-
-# Avoid trailing whitespace
-Style/TrailingWhitespace:
-  Enabled: true
-
-# Check for array literals made up of word-like strings, that are not using the %w() syntax
-Style/WordArray:
-  Enabled: true
-
-# This cop checks for numeric comparisons that can be replaced by a predicate method.
-Style/ZeroLengthPredicate:
-  Enabled: true
 
 #################### Metrics ###############################
 
@@ -135,81 +29,3 @@ Metrics/ClassLength:
 Metrics/BlockLength:
   Exclude:
     - 'spec/models/conference_spec.rb'
-
-#################### Lint ###############################
-
-# Wrap your assignment in condition if you mean it, otherwise it is most likely equality check
-Lint/AssignmentInCondition:
-  Enabled: true
-
-# Align blocks of code properly
-Lint/BlockAlignment:
-  Enabled: true
-
-# Things deprecated in current ruby API
-Lint/DeprecatedClassMethods:
-  Enabled: true
-
-# Do not use literal in conditions. We have it enabled for now
-Lint/LiteralInCondition:
-  Enabled: false
-
-# Prefer `Kernel#loop -> break` over `begin -> while`
-Lint/Loop:
-  Enabled: true
-
-# Do not put space before arguments when they are in parentheses
-Lint/ParenthesesAsGroupedExpression:
-  Enabled: true
-
-# Do not rescue Exceptions class itself
-Lint/RescueException:
-  Enabled: true
-
-# Do not shadow local variables in blocks, choose other name
-Lint/ShadowingOuterLocalVariable:
-  Enabled: true
-
-# Use _ or variable_name to explicitly mark variable as unused
-Lint/UnusedBlockArgument:
-  Enabled: true
-
-# Use _ or _argument_name to explicitly mark argument as unused
-Lint/UnusedMethodArgument:
-  Enabled: true
-
-# Avoid useless assignment
-Lint/UselessAssignment:
-  Enabled: true
-
-# Do not use variables in void context
-Lint/Void:
-  Enabled: true
-
-# Do not use duplicated keys in hash literals.
-Lint/DuplicatedKey:
-  Enabled: true
-
-#################### Rails ###############################
-
-# Enforce Rails specific style
-Rails:
-  Enabled: true
-
-# Use `find_each` instead of `each`.
-Rails/FindEach:
-  Enabled: true
-
-# Avoid use of old-style attribute validation
-Rails/Validation:
-  Enabled: true
-
-# Looks for delegations, that could have been created automatically with delegate method
-Rails/Delegate:
-  Enabled: true
-
-#################### Performance ###############################
-
-# Identifies places where gsub can be replaced by tr or delete.
-Performance/StringReplacement:
-  Enabled: true