Expose `cmp` as a prototype method

* Remove private comparator function
* Update method comment
* Update usage across lib to use new method (`eq`, `lt`, `lte`, `gt`,
`gte`, `pow`)
New minified build

* Built with uglifyjs
Update test suite for `cmp`

* Add `cmp` check in `T` assertion helper
* Add `cmp` comment references where appropriate
Add API documentation for `cmp` method
Added perf test for `cmp`
Added `cmp` support and usage doc to `bigtime`
Version bump (2.3.0) and doc updates

* Bump active version to 2.3.0
* Update changelog
* Add `cmp` example to `README`
Merge pull request #17 from loginx/make-cmp-public

Add `cmp` method