Improve LIKE/regex handling.

* Move handling of LIKE patterns to the compiler,
* add a `Search` functinon that takes a regex,
* add support for Postgres’ `~` operator (alias for `Search`),
* enable escape characters for LIKE patterns (fixes #65),
* change parsing of “suffixes” to be less hacky, and
* get rid of the `NotIn` and `NotLike` Binops and std lib functions.
Pull function names from StdLib rather than hardcoding strings.

Also

* eliminate the now-unused Between BinaryOperator, and
* add handling of `not` for `between`, and fix it for `in`.

Previous implementation would error if you tried using `not` in suffix
position for anything other than `like`.
Merge remote-tracking branch 'upstream/master' into ready/65-LIKE-escapes
Add new integration tests for LIKE and regex.
Merge remote-tracking branch 'upstream/master' into ready/65-LIKE-escapes
Merge pull request #379 from sellout/ready/65-LIKE-escapes

Improve LIKE/regex handling.