Update behavior for incoming SMS path.

1) On KitKat, unencrypted SMS messages are never stored in
   TextSecure unless it is set as the system-wide default.

2) On KitKat, if TextSecure is set as the system-wide default,
   provide an option to change the default to a different app.

3) Don't store the TextSecure challenge on KitKat+ devices.
Better support for local storage with passphrase disabled.

1) Never get into a state where messages aren't displayed
   unencrypted.

2) Fix bug where locked DB required launching twice.
Merge branch 'master' of https://github.com/WhisperSystems/TextSecure
Use modern icons in info and alert dialogs for ICS+
make bithub price update // FREEBIE

thanks lilia
Add contributing.md // FREEBIE

This file is recognized by github and presented to users who are trying
to open issues and submit pull requests.

Hopefully this more prominent placement will help deter people from
opening issues/prs for translation fixes.
Merge pull request #921 from liliakai/master

Add contributing.md // FREEBIE
Fix the send button's touch highlight color

Introduce a generic touch highlight background drawable, and use the
proper shades of blue (and gray on v19+).
Use the touch highlight background for the emoji toggle
Add touch highlight to contact photos
Use unified touch highlight in import & export
Replace the attachment dialog header icon with something modern
End conversation selection action mode if all deselected

This seems to be common convention in most apps.
Add missing spaces
a little typo mistake
fixed some hardcoded strings
Make default group avatar icon actually work.
Merge pull request #648 from veeti/tweaks-and-polish

Assorted tweaks and polish
Merge pull request #905 from benalbrecht/dialog_icons

Use modern icons in info and alert dialogs for ICS+
Show confirmation box before disabling push messages