Recommend use of JodaTime-Android for datetimes

[KishoreBabuIN]

This one is not a critical issue at this stage, but for easier code readability and general awesomeness I recommend we move all uses of SimpleDateFormat, and Calendar to equivalent DateTimes on JodaTime-Android.

Here's a link to know more about JodaTime-Android: https://github.com/dlew/joda-time-android

I can submit a pull request if you agree with this.

Cheers.

[Yuncun]

Hi. Adding jodatime was one of my to-dos and I would certainly accept a pull request if you are interested. Otherwise I will get to it in the coming weeks.

Most of it should be easy but I do do some weird stuff with dates at some points. I'll take a look at the current state of the app in the coming week and follow up on this.

Thanks