fix podspec lint warnings

I have added KSCrash to public podspecs repository. So, now  "pod search KSCrash" works.
Link is here:

https://github.com/CocoaPods/Specs/blob/master/KSCrash/0.0.1/KSCrash.podspec

To do so, I was faced with KSCrash.podspec "pod spec lint" warnings. This commit just fix all warnings in existed podspec.

Podspec is updated as well (https://github.com/kstenerud/KSCrash/issues/35)