Lavi - 1.9.0

Features:
- [Str] add reverse() function ( #238 by @yivi )
- [Str][Grapheme] add reverse() function ( #239 by @yivi )
- [Fun] add tap() function ( #234 by @veewee )
- [Type] performance improvements ( #223 by @Ocramius )

Other:
- add benchmarks ( #223 by @Ocramius )
- add documentation functions to makefile ( #235 by @veewee )