`flit_bisect.py` file is too large

[mikebentley15]

The flit_bisect.py file is starting to get unwieldy because it is getting too large at approximately 1800 lines. Much of that is doctest strings, but still. So one could either separate out the doctest strings into the automated tests directory, or move some functions to another file. I'm imagining another file called bisectsearch.py containing the algorithms and functions specific to the basic algorithms, and have the command-line and control logic still within flit_bisect.py.