fix(install): dirs in stores can't contain colons

Close #479

src/resolve/git.ts

@@ -9,7 +9,7 @@ export default async function resolveGithub (parsedSpec: PackageSpec, opts: Reso
   const repo = parts[0]
   const ref = parts[1] || 'master'
   return {
-    id: parsedSpec.spec.replace(/\//g, delimiter),
+    id: parsedSpec.spec.replace(/[\/:]/g, delimiter),
     fetch: (target: string) => {
       return clone(repo, ref, target)
     }