added init defaults, set single method
handling for presentation vs dismissal
Updating all transtion methods to have
single call for dismissal and presentation
keying off of isPresenting flag
refactored code to utilize helper method
blocks created for VC animations
using isPresenting flag wherever possible
created flags for delay and implemented in code
refactored code and added methods to
set and use the custom transition durations
Merge pull request #3 from Javier27/customDurations

added init defaults, set single method