Add spec test for libsass issue 703

https://github.com/sass/libsass/issues/703
Add spec test for libsass issue 701

https://github.com/sass/libsass/issues/701
Add spec for new colors (rebeccapurple and transparent)

https://github.com/sass/libsass/issues/699
https://github.com/sass/libsass/issues/700
Add specs for issue 702
Merge pull request #158 from mgreter/spec/issues/703

Add spec test for libsass issue 703
Merge pull request #159 from mgreter/spec/issues/701

Add spec test for libsass issue 701
Merge pull request #160 from mgreter/spec/issues/700

Add spec for new colors (rebeccapurple and transparent)
Merge pull request #161 from xzyfer/feat/issue-702

Add specs for issue 702
Move passing test out from todo folders
Restore another test (expected_output was missing)
Added spec for fixed if function
Added spec for negative indexes in nth function
Merge pull request #166 from HugoGiraudel/add_spec_negative_indexes

Added spec for negative indexes in nth function
Merge pull request #165 from HugoGiraudel/add_spec_fixed_if_function

Added spec LibSass issue 338
Merge pull request #163 from mgreter/move-passing-tests

Move passing test out from todo folders
Update spec for feature-exists for sass compat
Merge pull request #172 from xzyfer/fix/issue_702

Update spec for feature-exists for sass compat