Update deployment target for project. to 7.1

We are only targeting iOS version 7.1 which is the latest version. The
project file should have this set as the default rather than older
versions.
Add icons to plist template
Normalize tabs in plist file.

Most of our editors are set to prefer spaces over tab characters and
since this is a template file that we edit frequently with standard text
editors it makes sense to reduce noise by swapping the tabs for spaces.
Merge pull request #206 from lliss/topic/update-deployment-target

Update deployment target for project. to 7.1