Allow the user to stop execution of the program.

This requires the programmer to take a multithreaded approach and call
brainfuck_execute from a separate, non-main thread.
Merge pull request #28 from SevenBits/master

Allow the user to stop execution of the program.
Update contributors
break token
Merge pull request #29 from durka/breakpoint

breakpoints
Update CMakeLists.txt
Update CHANGELOG.markdown
Update README.markdown
Update version
Fix wrong version
Update CMakeLists.txt
Change to MIT license
Rewrite source
Fix consistency and comments
Fix consistency and comments
Start of brainfuck 3.0.0
Brainfuck 3.0.0