Added Rubocop

The HashSyntax cop is turned off since we still support ruby 1.8.7

This pull request start the fix for #24.

I did some styles fix (just simple stuff) on some classes, but there is some i didnt know how to fix like:

```shell
 lib/fog/storage.rb:37:9: W: Do not suppress exceptions.
        rescue # ignore any missing credentials/etc
 lib/fog/storage.rb:24:16: C: Do not use :: for method calls.
            Fog::const_get(Fog.providers[provider])::Storage
 lib/fog/storage.rb:57:34: C: Use && instead of and.
      if data.respond_to?(:path) and !data.path.nil?
```