Cache tweets for the detailed view

[garrett]

When tapping on a tweet, it always reloads the tweet in the next view. This is annoying on cell data, especially when on a bad connection (such as on GRPS-level-speed).

[gena01]

I noticed this also when I don't have reception (try taking underground subway in NYC). Tend to set "Airplane" mode and the screen won't load at all, at least it doesn't crash. Using latest 1.1.2 version.

[BlythMeister]

To correctly do the corners for #77 this needs to be done.
Since you can rt and star in the spotlight.

[BlythMeister]

fixed by #128