Remove usage of DBL_MAX and -DBL_MAX

Fixes compile errors on GCC. std::numeric_limits<double>::min() and
std::numeric_limits<double>::max() is apparently the new C++ way of
doing things.
Add CMakeFiles to .gitignore
Merge pull request #1 from ahockersten/ahockersten/compile_fixes

Compile fixes for gcc/ubuntu + gitignore additions