Add timesHeapContainer with tests

Add timesHeapContainer with tests

timesHeapContainer is a slice based implementation of heap.Interface
for requestTime structure (combines time.Time with ReqID).
Defined type is required for creating a heap of time structures with
additional data identifying request related to the time.
It will be used by requests package for getting minimal ValidAfter,
Deadline and Timeout times of requests. The special goroutine will
notify request-worker matcher, when proper time comes.

Change-Id: I2b71f84d2f3843bb47c0c9b7c7279ca224fba64b
Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>