Revert "Strict matching for not operator"

This reverts commit 70d70e47c752744a4035517f548d37c2c509adec.
Revert "Merge pull request #658 from xzyfer/wip/not-expression"

This reverts commit b2f57a759c28e55f86560cd33e11844d9dd637aa, reversing
changes made to c0dbb431c99c0cf2bba7f79c76892a561cba7b26.
Merge pull request #661 from xzyfer/revert/not-expression

Revert not expression
Hotfix for new API and error not being re-thrown
Fix for potential segfault
Fix conversion between unit and implement angles
Merge pull request #667 from mgreter/bugfix/unit-conversion

Fix conversion between unit and implement angles
Fix possible segfault (init importer in old API)
Update sass2scss to latest version (1.0.2)
Fix possible segfault (init importer in new API)
Add minimal protection from calloc/malloc errors
Revert unneeded fix