Rework timer store to reduce internal state
Get UTs to compile
Delete tests that peek into the TimerStore's internal state
Fix bug causing long timers to pop at the start of the second they were due to pop in
Fix UTs
Add test that timers in different stores but with the same pop time, do actually pop at the right time
Check timers can pop corrctly on the hour
Markups
Fix compiler errors
Merge pull request #34 from Metaswitch/issue32

[Reviewer: Andy][From: Alex] Timer store rework (fixes #32)
Fix valgrind errors
Merge pull request #35 from Metaswitch/issue32_vg

[Reviewer: Andy][From: Alex] Fix valgrind errors.
Update cpp-common
Add failing tests for overdue timers
Handle overdue timers
Improve commenting
Update cpp-common
Markups
More markups
Merge pull request #38 from Metaswitch/already_popped_timers

[Reviewer: Rob][From: Alex] Cope with timers that have already popped more gracefully.