Merge pull request #34 from xyproto/master

Minor changes to the instructions
added PNG optimization commands
Merge pull request #37 from Jesin/master

added PNG optimization commands
added ick optimization flags
invoke ${CC}/${CXX} instead of tcc/gcc/g++
using gcc explicitly for ObjC; fixed README.md
Merge pull request #38 from Jesin/master

added ick optimization flags; invoke ${CC}/${CXX}
* NO_PNG_OPT=1 disables PNG optimization.