Update PSM Date and Time to be Selectable Instead of Text

No Issue (Yet)

I updated the date and time inside the post settings menu so that it can be selected via calendar or using up and down arrows, etc. Thought it might be easier than having to type in the date with the @ time etc.

![screen shot 2014-11-13 at 1 31 17 pm](https://cloud.githubusercontent.com/assets/4715098/5037046/6a295c26-6b39-11e4-8012-9d0062ecd304.png)
![screen shot 2014-11-13 at 1 31 23 pm](https://cloud.githubusercontent.com/assets/4715098/5037045/6a2708c2-6b39-11e4-9d95-14302eb28160.png)

I have tested it a little bit and believe it is working and haven't had any problems with saving or new posts.

I can create an issue and update the PR if this is something that you want merged. If not, just go ahead and close.
This selector needs to be added to line 147 too. :)