Add documentation to the Stopwatch js file.
Add documentation to the Stopwatch js file.

- Detailed documentation with appropriate constructs for parameters,
  and return values, for each method.

Signed-off-by: Siddharth Kannan <805f056820c7a1cecc4ab591b8a0a604b501a0b7@gmail.com>

MickCrozier/timer-stopwatch,paulkass/timer-stopwatch-1