Remove Python bytecode

The notion that Python is a fully interpreted language isn't exactly correct. As an optimization, the interpreter will compile the source files into bytecode, so it doesn't need to interpret that code directly each time its run. It's pretty easy for the bytecode files to get out of sync with their cooresponding source files, so it's considered a best practice to not include these files in repositories.

This commit:

* Removes all .pyc files.
* Adds a .gitignore file with rules preventing various forms of Python bytecode from being added in the future.