NSArray Properties to Copy Ownership, and Retains/Releases

Hello,

In using your wonderful SVSegmentedControl library, I noticed a couple of issues.  First, the NSArray properties in the SVSegmentedControl class have strong/retain ownership… generally one wants copy ownership here to avoid issues with the array changing size or its elements at awkward times.

Second, there were some missing retain/releases in some of the custom setters.  I've added those that I spotted on a quick glance.