Adds keyboard panning offset corrections. Based on @efremidze implementation.
Fixes keyboard panning when reaching to the bottom of the screen. Adds text view pan gesture (missing implementation). Renames SCK to SLK class prefix
Makes text view become first responder with custom pan gesture
Uses -viewDidLoad instead of -loadView for setting up subviews and view constraints (works better for Storyboards)
Merge pull request #43 from slackhq/keyboard-panning-fix

Keyboard Panning Fixes. Closes #41