Rewrote almost everything.

I need to port the important function, the one that actually manipulates tmux.
This is a pretty good method of handling the configuration, though some things
are still bothering me.
Re-implemented the start command.

It's a bit nicer than the original, but I'll be doing some more clean up.
Altered access to the run context.
Switch sessions when inside a tmux session.

Fixes #4
Made the verbosity configurable.

Setting the TENPER_VERBOSE environment variable to 'true' will cause tenper to
print out all the commands it executes.
Added project classifiers.
Version bump; added a change log (changes.rst).