add documentation, some code cleanup, and a bug fix

[js850]

After seeing Jasper Snoek talk in cambridge I was inspired to try this bayesian optimization package. It seems well written and well commented, but without much documentation. I had a some difficulty trying to understand what all the variables meant and what all the routines were doing. So while I was going through the code in detail I added some documentation for my own benefit. Maybe you guys will appreciate it. But please go over my documentation carefully. The only thing worse then no documentation is incorrect documentation.

I also made some other changes.

1. I did a bit of code cleanup, like removing tabs, removing unused imports, changing 2-space indents to 4-space, shortening long lines, etc.
2. I added a new example for noisy functions. This is simply the branin function with some added noise.
3. I added a file make_plots.py to the simple branin example. Using your README I was able to easily run the example, but I had no idea what to do then. I didn't know how to access the data or make predictions or find the best guess for the minimum, or show uncertainties. make_plots.py is basically my solution to that, though it may be a bit hacky. You may want to update it if there are more elegant ways of doing this. I wrote it in a general way so it can be called from any experiment directory with a 2-dimensional function (e.g. examples/noisy)
4. I restructured main.py, separating out the part that reads in the options. I did this mostly because I wanted to re-use it for make_plots.py
5. I renamed some variables because I found it really hard to know if variable tasks referred to a list of Task objects or a list of task names (strings). This confused me a lot and I only changed a few of the examples.

Finally, thanks for the great code

[js850]

Oh, I forgot to mention that the very minor bug was in DefaultChooser where grid_size and grid_seed were not being used.

[JasperSnoek]

Thanks Jacob! Yes, this repo is in dire need of better documentation. Thanks for doing this! I'll review this as soon as I can (along with @mgelbart and @kswersky).

In the meantime, in order to pull this in we'd need you to agree to the contributor license agreement. If you agree could you indicate that you do in this thread?

[js850]

I agree to the contributor license agreement.

[mgelbart]

I will review your changes soon and get back to you. Thanks for contributing all this useful documentation!