543 home page ui tweaks

[DO NOT MERGE] hey @pld, i would appreciate feedback on the approach I used to make the ajax requests
to abstract pulling out the url you should use the simpler [`get-event`](https://github.com/onaio/zebra/blob/master/src/cljs/ona/api/io.cljs#L16) method.

You'll have to extend this with a multi-method to take a query-params arg.