Fix mixed tabs and spaces

Until now we have had a haphazard mix of spaces and tabs throughout the code. Since there seemed to be a heavy preference for 4-space indenting rather than tabs. Everything has been converted to spaces. There was no code changed here, only whitespace.

Because this is a whitespace only change, the git diff tool isn't the most helpful way to verify that no code was changed. Here is a side-by-side diff that helps demonstrate that no code was actually changed: http://www.diffchecker.com/3vm3rw2v