add About section

app/src/main/java/com/simplemobiletools/camera/AboutActivity.java

@@ -0,0 +1,52 @@
+package com.simplemobiletools.camera;
+
+import android.content.res.Resources;
+import android.os.Bundle;
+import android.support.v7.app.AppCompatActivity;
+import android.text.Html;
+import android.text.method.LinkMovementMethod;
+import android.widget.TextView;
+
+import java.util.Calendar;
+
+import butterknife.BindView;
+import butterknife.ButterKnife;
+
+public class AboutActivity extends AppCompatActivity {
+    @BindView(R.id.about_copyright) TextView copyright;
+    @BindView(R.id.about_version) TextView version;
+    @BindView(R.id.about_email) TextView emailTV;
+    private Resources res;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_about);
+        ButterKnife.bind(this);
+        res = getResources();
+
+        setupEmail();
+        setupVersion();
+        setupCopyright();
+    }
+
+    private void setupEmail() {
+        final String email = res.getString(R.string.email);
+        final String appName = res.getString(R.string.app_name);
+        final String href = "<a href=\"mailto:" + email + "?subject=" + appName + "\">" + email + "</a>";
+        emailTV.setText(Html.fromHtml(href));
+        emailTV.setMovementMethod(LinkMovementMethod.getInstance());
+    }
+
+    private void setupVersion() {
+        final String versionName = BuildConfig.VERSION_NAME;
+        final String versionText = String.format(res.getString(R.string.version), versionName);
+        version.setText(versionText);
+    }
+
+    private void setupCopyright() {
+        final int year = Calendar.getInstance().get(Calendar.YEAR);
+        final String copyrightText = String.format(res.getString(R.string.copyright), year);
+        copyright.setText(copyrightText);
+    }
+}