Added .gitignore

Added c++ gitignore to avoid tracking binary files.
Inspired by the github/gitignore repo
https://github.com/github/gitignore/blob/master/C%2B%2B.gitignore
also ignore profiling compiled binary
also ignoring analysis.txt
Makefile only compiles if the file has changed

Fix makefile syntax so that it compiles the program only if the source has
changed since the last compilation.
Merge pull request #2 from Enucatl/master

Added .gitignore