Using Travis CI.

This PR contains Travis configuration file, which allows to build this project simultaneously on several configurations using build matrix. The matrix contains the following options:

 - OS: Linux, OSX (need to enable manually by writing email to Travis Team).
 - Build type: debug, release.
 - C++ Standard: c++0x, c++11 (OSX build allows to build only with c++11).
 - Build configuration: regex tests and main examples.

Don't forget to add Travis badge to README.md.

Build sometimes fails in https://github.com/3Hren/benchmark/blob/master/src/benchmark.cc#L1130, I don't know why yet. Please, check it.

Also this commit closes #61.