Add all the checks!

After watching Dr. Rian Quinn's "A Test a Day Keeps Your Manager Away!" and looking over https://github.com/ainfosec/ci_helloworld, added checks for whitespace, ClangFormat, ClangTidy, Valgrind, Coverity, and CodeCov.

Also re-organized CMakelists.txt according to current best practices outlined in https://github.com/Lectem/cpp-boilerplate/blob/master/CMakeLists.txt.