Fix display of repeated events in the "upcoming" view.

#6359 

This PR addresses https://github.com/openscholar/openscholar/issues/6359#issuecomment-48739660.

Before the change:
![selection_356](https://cloud.githubusercontent.com/assets/4497748/3564364/b35feeb0-0a80-11e4-966b-d94907fe0d43.png)

After the change the "upcoming events" view displays the correct date for the repeats:
![selection_355](https://cloud.githubusercontent.com/assets/4497748/3564368/cda90df6-0a80-11e4-914d-853250e194b1.png)