use string class functions instead of strstr

If we already have strings then we should stick to them instead of using
C-functions
more std::string goodness
use c++11 foreach loop

C++11 introduced a foreach style looping for classes with iterators. If
we enable these features by default for compiling we should make sure to
use them to make the code better readible
Merge pull request #135 from kain88-de/c++_idioms

I'm not so keen on the string comparison, but otherwise that's fine.