Added context support to callback
Updated examples and docs
fixed cast for callback
Update ReadMe.txt
Timer::stop returns TIMER_NOT_AN_EVENT when timer was stopped
Changed the stop() method to return TIMER_NOT_AN_EVENT when it is given a valid timer event ID.  Given an invalid (out of bounds) ID, it simply returns the same ID that it was given.
Converted the ReadMe file to Markdown, added examples, reference, etc. from Dr. Monk's site.
Minor cosmetic editing, tabs to spaces.
Closes #5.
use predefined constant instead of magic number
Merge pull request #6 from ThoMo/master

use predefined constant instead of magic number
Merge remote-tracking branch 'origin/v2.1'

Conflicts:
	ReadMe.txt
	Timer.cpp