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