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)
V2.0 Support for IE conditionals within block

Support in V2.0 for IE conditionals within blocks, either on same line
or within the block. No issues found with indentation or positioning.

Added Fixtures and Tests.
Backported PR #173
Update README.md
Merge pull request #181 from RWOverdijk/patch-1

Update README.md
Merge pull request #168 from zeppocreative/v2.0

V2.0 Support for IE conditionals within block
Merge branch 'v2.0'