Fixed possible race condition
oops! You can't do a mutex lock on a nil variable, unsurprisingly, so previously this was innefective at preventing the possible race condition (I've never seen it though).
adding podspec
fixed podspec
added binding convenience constructor
podspec typos
added podspec and also Podfile to make the test apps easier to build
updated readme and typo
renumbered tests and now using libextobjc for retain cycle avoidance
improved tests
added test for binding
fixed a case where the swizzled dealloc wouldn't remove binding due to weak ref having gone nil already