Sort Events before Mapping, fixes #125

This PR sorts events before they're sent to be made into the map. This will help exposes as best it can new events that would otherwise be hidden by other markers: 

https://github.com/nodeschool/nodeschool.github.io/issues/125

@brianloveswords I don't think we can actually get the marker on top of ones more south on the map because of positioning. If the NYC marker was on top of one in Georgia then the point of the NYC's would be on a marker. So I think this may be the best we can do. Anyone else have an idea?

PS—This also does a little bit of cleaning up of spacing in the event list.

Before:
![screen shot 2014-10-29 at 8 28 16 pm](https://cloud.githubusercontent.com/assets/1305617/4834238/d19895f0-5fab-11e4-9a35-849e1c7ce7fd.png)

After:
![screen shot 2014-10-29 at 8 28 23 pm](https://cloud.githubusercontent.com/assets/1305617/4834245/dba43964-5fab-11e4-8f98-fac0e31e2847.png)
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