test => call once
test => call once
test => pass args
test => move fixture into setup()
fix bug => return undefined in subsequent call
refactoring => using flag called instead of array stack
Merge branch 'once'
add test into all-tests.html
test => subscribe
test => subscribe invalid handlers
refactoring => move fixture into setup()
test => subscribe handlers
test => emit
test => handler context
test => pass args on handlers
test => unsubscribe
test => unsubscribe handlers
test => unsubscribe last handler
test => make emit,subscribe,unsubscribe public only
test => extract each method