Allow for multiple different compilers to be used to run tests (msvc & gcc support) #27

Based on what I've seen with this library the only C compiler that llparse-test-fixture currently accepts is clang/llvm. I was wondering if it would be a good idea to add in support for msvc & gcc likewise. These shouldn't be too hard to implement and should give users a little bit more freedom with what other compilers can be used when running tests locally or offline.