updated changelog
Bump version: 0.2.13 → 0.2.14
tried making DCP recursive, but disasterous for performance
Revert "tried making DCP recursive, but disasterous for performance"

This reverts commit dc886ae33c23ee914f31af19bf8dbdd929108d59.
tried to clean up monotonicity evaluation, too much work
Revert "tried to clean up monotonicity evaluation, too much work"

This reverts commit 9b5d9d86aa63a32081fad22b38a3d9afde15482b.
added init_dcp_attr method to AddExpression