Fix compilation for G++4.7 on Ubuntu 13.04

Ubuntu is shipped with G++4.7
To run Bandit specs with G++4.7, I needed to:
 * update compile flags via CMakeLists.txt
 * add <stdexcept> header to bandit.h (otherwise, got and error with assertion_exception.h)
 * add <string.h> header to specs/util/argv_helper.h in order to use strlen