Grunt 0.4 ready with bugfixes

Hi, since I needed Grunt 0.4 support urgently I applied the patch from @tony and also made a few code changes:

- reghtml was matching all attributes that followed href/src within the tag once I removed the "/" requirement since I needed both relative and absolute path matches. So I have fixed that and also simplified the matching expression.
- if options.flatten is true all relative paths are flattened, essentially making all "../" same as "/"
- updated docs and config files to make this plugin 0.4 ready
- version bumped.