Swift 4 + 2 important fixes

The lib version matches that of the Swift langage. Hence the move from 3 to 4, despite having only small changes.

But #33 is fixed, and you can now add tabs on the flyw without problems. And more importantly, they appear correctly, since another bug hidden by that first one, is also fixed.

KPCTabsControl takes the Swift3 train!

KPCTabsControl has been migrated to Swift3. No changes of APIs compared to the 2.0 release, written with Swift 2.2. Possible future of Swift2 releases will be placed on the new swift-2.2 branch.

Various bugfixes

• Introduction of a dedicated control cell to fix a problem when clicking outside the last button
• Changed hard-coded Helvetica fonts to system ones
• Fixed a method typo (1.6.2)
• Fixed an issue with autolayout (1.6.1)

Fixed Editing

Editing of tab titles wasn't working, and the demo didn't allow to play with it. This is now fixed, and some other details have been improved as well.