new shinier documentation

- npmingore gets rid of docs and tests in package
- all docs converted to rst
- everything is working on readthedocs.org
- :rabbit:
Merge pull request #410 from jenius/v3#docs

Better Docs
base template is now 'roots-base'
use antimatter for command line docs
prerelease rc3 :shipit:
makefile bugfix, closes #411

The Makefile was only copying over coffeescript and in the
process dropping any other files on build. This commit
fixes that.
add v3 beta support note to readme
refactor extensions to be scoped to categories
stub out test cases for extension failures
update extension documentation
update install instructions, link docs in readme
add tests for category scoping functionality

- fix a couple bugs in the process
- test cases for overrides and skipping categories as well
tests for extensions failure points
thorough edit/polish of extensions documentation
Merge pull request #413 from jenius/v3#simplify-extensions

Better Extensions API
fix small bug with write hook

file extension is only set if it isn't already overridden by
a roots extension
prerelease rc.4 :shipit:
add docs for compilation
start work on features/comparison docs
fix: move util require to top