Adding support for conditional comments. Fixes grunt-usemin issue #119.
Adding tests for conditional comment support.
Merge pull request #137 from kavanagh/master

Adding support for conditional comments.
Usemin v2.0: simpler, more powerfull

Invoking the wrath of the git gods by squash the commits of this branch !!!
Forward port of PR #106 and #141

Support of media and defer attribute are now working on v2.0 as well.
Fix README typo
Flow is now properly defined by build type fixing #149 and #143
fixed typo
Look for both prefixed and suffixed revved files (fix #153)
Support multiple targets in useminPrepare