Remove unused variable
Use `'utf8'` instead of `'utf-8'`

This follows the Node.js convention. See http://nodejs.org/api/fs.html.
Add tests for local `Identifier`s within `MemberExpression`s

Ref. #9.
Don’t rename local `Identifier`s within `MemberExpression`s

Fixes #9.
README: Update browser support
Update coverage report
Tag the v0.2.3 release