Update M13Checkbox.m

CheckView contained a retain reference to M13Checkbox, and M13Checkbox contained a (default) strong reference to CheckView, creating a retain cycle and a memory leak. Changing CheckView's reference to M13Checkbox to weak fixes this retain cycle.
Merge pull request #10 from UberJason/master

Fix retain cycle in CheckView
Added IBAction Example
add gitignore to avoid dirty repo
upgrade deployment target to 7.0
use assets catalog from now
replace deprecated method sizeWithFont: by sizeWithAttributes:
update deprecated setState method by setCheckState:
update deprecated toogleState method by toogleCheckState
upgrade iphone / ipad xibs version
remove dirty and useless user/pod files
remove .DS_Store
avoid warning by using CGFloat instead of float
remove empty Podfile
Merge pull request #12 from james075/master

clean / update project to the latest SDK
Major Update

* Cleaned up code.
* Changed text handling for more control.
* Changed check size handling for more control.
* Added app icons and launch images
Removed default images
Updated MIT License
Merge remote-tracking branch 'upstream/master' into develop

Conflicts:
	.gitignore
	Classes/M13Checkbox.h
	M13Checkbox.podspec
	M13Checkbox.xcodeproj/project.pbxproj
	M13Checkbox/ViewController.m
Make it work with iOS 6.0