Updated boost to version 1.53.0
Updated .gitignore
Updated build script
- script now auto-builds boost 1.54.0
- script now auto-builds boost 1.54.0
- made sure to ignore downloaded and build files for boost 1.54.0
- reverted to boost 1.53.0 as 1.54.0 seems to have issues on iOS
- now compiles with GCC instead of libc++
Fixed flags