Classes using Julia: lexographical ordering and geo information

[carstenbauer]

See #764. This PR does the following:

• merges multiple separate entries of same institution
• sorts lexographically by institution name
• puts time information (i.e. "Fall 2015") on course rather than institution
• adds (approximate) geo location (latitude and longitude) to institutions in the form of invisible html comments. This is a preparation for integrating the interactive map (see http://github.com/crstnbr/juliamap).

I hope the html comments containing the geo information are really hidden. Github preview says they are but I couldn't check because I don't have Docker available.

[carstenbauer]

Of course, it's also fine to have entries with no geo information. They will end up as missing and will be ignored in plotting the map (see https://github.com/crstnbr/juliamap/blob/master/juliamap.jl)

[ViralBShah]

Let's see how this feels.

[carstenbauer]

Feels good to me :)