Added Persistence feature
Turned off COUNTLY_DEBUG and added compiler flag when COUNTLY_DEBUG is enabled to prevent unused variable usage.
Merge pull request #22 from nesimtunc/master

Added Persistence feature
Update README for persistence
Updated README for Persistence
Merge README.md
Updated README for Persistence
Merge pull request #24 from nesimtunc/master

Updated README for Persistence
fix mentioning of disabling arc for countlydb.m
Added pragma marks
Defined constants DEFAULT_UPDATE_INTERVAL & EVENT_SEND_THRESHOLD
Improved namespacing by adding Countly prefix to DeviceInfo, EventQueue & ConnectionQueue
Adopted Allman style indentation
Improved thread safety of singletons by using dispatch_once
Simplified GTMNSStringURLArgumentsAdditions category as Helper Functions
Added CountlyDeviceInfo method definitions
Improved metrics method by using dictionary and serialization
Improved events method by using dictionary and serialization
Fixed integer warnings
Cleared useless @synthesize directives
Replaced some instance variables with properties
Fixed managedObjectContext accessors
Used new literals to create NSNumbers
Fixed memory leaks
Changed default value of IGNORE_INVALID_CERTIFICATES to 0
fixed CountlyDB error logging