Add progress bars and FIt-sne

[saketkc]

This PR does the following

• Replaces print with progress bars (Demo: https://gist.github.com/saketkc/708d8f03b8d42090fd3dd4a8ff8feba5)
• Adds FIt-sne as a layout option (https://github.com/KlugerLab/pyFIt-SNE)

[duhaime]

@saketkc Thanks very much for this PR! I love the progress bars, and very much like the idea of the fitsne.

I wanted to ask, though, how do you feel about making the fitsne library an optional dependency? I ask because it has a dependency on header files that are not shipped with the library itself. We could create utils/fitsne-dependencies.txt and list fitsne there, so those who want to kick the tires have an easier time getting started. @pleonard212 and I just discussed the notion of creating a similar utils/gpu-dependencies.txt for those who want to run the processing with GPU-acceleration. We'd just want to update the README to tell users how to use the fitsne layout, and wrap the import statements in utils/process_images.py in a try/catch block.

I also wanted to ask, what is config? You pass it to the tf.Session constructor but it doesn't seem to be defined.

Last, what do you think about adding progress bars for the print statements you commented out? I think those could be nice to have...

[saketkc]

Thanks @duhaime! I have tried to address your comments:

• Made fitsne optional
• Added utils/fitsne-dependencies.txt
• Cleaned up config which was unused from tf.Session

[duhaime]

Sorry for the insane delay on this @saketkc. I'm just circling back now and this is fantastic! Thanks very much!