Don't split a block with @at-root unless necessary.

Closes #1239
Merge branch 'stable'

Conflicts:
	VERSION
	doc-src/SASS_CHANGELOG.md
	test/sass/scss/scss_test.rb
Merge remote-tracking branch 'origin/stable'
Merge remote-tracking branch 'origin/stable' into stable
Merge branch 'stable'
Fix a failing string-parsing test.
Merge remote-tracking branch 'origin/stable' into stable
Updated Number Operations for Unit Math

See [multiplication error](https://github.com/nex3/sass/issues/83). This comes up all the time and the current documentation implies that Sass will do unit conversion for them for everything.
Fix a sass-convert comma-folding bug.

Closes #1257
Fix @media interpolation errors.

Closes #1260
Merge pull request #1261 from Snugug/stable

Updated Number Operations to include Unit Math
Merge remote-tracking branch 'origin/master'

Conflicts:
	doc-src/SASS_CHANGELOG.md
Merge branch 'stable'

Conflicts:
	lib/sass/selector/comma_sequence.rb
	lib/sass/selector/sequence.rb
	test/sass/scss/scss_test.rb
:nth-match has been folded into :nth-column.

:column() has also been replaced by "||". This removes the :column
tests; "||" support will be added later.
Merge remote-tracking branch 'origin/stable' into stable
Bump VERSION to 3.3.8.
Merge branch 'stable'

Conflicts:
	VERSION
	doc-src/SASS_CHANGELOG.md
Fully parse selectors nested within pseudoclass selectors.
Add some failing tests for selector pseudoclass extension.
Add superselector support for selector pseudoclasses.

This also adds a new superselector test file.