Document "ignored" blocks

If using a block type other than `js` or `css` the block will be "ignored" and replaced by an empty string.  This behaviour is enabled by fixes in #303 and I believe it should be documented because it is incredibly useful for including development-only scripts that you don't want to include in your production build, e.g. Angular's mock http service and a script that you use to configure it.
Update dependencies.
Merge pull request #363 from robertjd/master

Document "ignored" blocks
Update README.md

Updated documents to reference grunt-filerev instead of grunt-rev.
Merge pull request #376 from justinrknowles/fix-docs

Update README.md
Update debug module.
Bump to new version
Skip duplicate configurations.

This should resolve #289.

This also detects a bad configuration where multiple blocks attempt to write
to the same destination with different sources.
Update file.js

Fixed conditional regexp to handle cases like <!--[...]><!-->
Merge pull request #383 from ppavell/master

Fix for Conditional Comments Mangling #263
Updating regex to fix conditional mangling

fixes #263 ??

Slight edit to regex so that comments can still be on same line
Merge pull request #384 from zeppocreative/master

Updating regex to fix conditional mangling
add suport for block replacement for custom block types
Update dependencies.
remove self-closing in link tags
fix linebreaks in README.md
Merge pull request #337 from mcampo/custom-types

add suport for block replacement for custom block types
Merge pull request #382 from boushley/skip-duplicates-289

Skip duplicate configurations.
2.3.0
Update README.md
Merge branch 'master' into patch-1

Conflicts:
	README.md