Added helpshift prompt for repeated login failures

As most of our bad reviews come from users unable to login, it seemed like adding a button to allow quick access to Helpshift was worthwhile. Here's a screenshot:

![contact us](https://cloud.githubusercontent.com/assets/437043/3491454/18c0974e-0592-11e4-832e-79936f0d5a27.png)

Oh, I just meant a `NSLocalizedString` description for the polyglots