Turn some constants into properties on TIToken, in order to use them in a subclass
Add a TIToken subclass, TIFlatToken, that's used by TITokenField optionally.

It is used by default if the user's device is running iOS 7 or later, but you can set
TITokenField's useFlatStyle property to explicitly set whether you want it used or not.
Draw "flat tokens" the way they appear in Apple's apps on iOS 7

This means that non-selected tokens appear coloured with no background and include
a comma in their title. Selected tokens appear white on a solid background with ~3px
radius corners.
The disclosure arrow should be a little bit thicker, shorter, and grey.
Merge branch 'master' into ios7-style-2

Conflicts:
	TITokenField.m
Updating podspec
Merge pull request #14 from sadlerjw/ios7-style-2

Implement iOS 7 style for tokens