epiViewcontroller startStop call epiBlinkModel startBeat on first call
Refarctor epiBlinkModel on period property declaration
epiBlinkModel isStarted is false after init
isStarted is true after call start
isStarted is false after stop call
Refactoring: isStarted is computed from thread fields
epiViewController viewDidLoad set title of button StartStop
Reorganize source code (add separator line)
Refactoring test blinkControllerTests