simplify makefile
add unit tests for os_zlib
import zlib-1.2.8
compile linux version with zlib-1.2.8
update os_zlib interface
use more stricter compile flags for tests
comment change
clean up comments
update zlib test binary
fix conversion warnings
let travis run tests
install required check library
build windows with zlib 1.2.8
remove zlib 1.2.3
fix missing zlib files for windows
Merge pull request #133 from cgzones/os_zlib

os_zlib update