Fixed a type in documentation

SassScript now supports **seven** data types since 3.3, not *six*.
Merge pull request #1526 from HugoGiraudel/stable

Fixed a typo in documentation
Fix typo in documentation
Merge pull request #1532 from nakadai/fix-typo

Fix typo in documentation
Fix interpolation conversion in calc().

Closes #1537
Fix @extend !optional conversion to SCSS.

Closes #1538
Don't add extra whitespace when converting @at-root to SCSS.
Make some conversion tests more robust.
Don't crash on selectors containing escape codes.

Closes #1541
Compatibility with listen >=2.7.12.

enough for a release.
Fix listen tests.
Fix source_map_test.
Bump VERSION to 3.4.9.
corrected the docs
Merge pull request #1544 from rishijain/update_docs_1

corrected the docs
move compiler_test.rb to where it should be
prepare listen wrapper for extracting into gem
include compliant test files in Rubocop