Revert "readme: Add Rails 3 notice"

This reverts commit 0f37b4d4ffb3bb50551489aa8763fc5a548e59ea.
converter: better apply_mixin_parent_selector
rake convert
readme: notice about rails 3.2.x pipeline stuff
a simpler solution to #523 rails 3 compat
bump to 3.1.0.2 + changelog
readme: simpler copy command
travis: bump sass-head
converter: default &:extend() to all
rake convert
rake convert
converter: new grid patch + rake convert
readme: Sass number precision requirement. See also #409
Update README.md
rake convert