[$30] - [Bug Hunt - NEW BUG]Can't handle invalid date properly

[twicoder]

1. Open URL
   http://community-app.topcoder.com/challenges/?filter[text]=&filter[endDate]=99999999999-09-01T04:00:00.000Z
2. The date is invalid, but it should be handled properly

[birdofpreyru]

Accepted, 3 points.
Indeed, we should validate that dates suggested in URL query are proper, otherwise, ignore them and remove corresponding element of the query.

[twicoder]

ready for review, PR #272