fix resizing collisions caused by asynchronous nature of scope.$watch

[Merott]

The resizing sometimes wouldn't work as expected because resize was being called at different times with different values, and not always the most recent would win. By implementing a short delay, and ensuring that previous calls to resize() are cancelled, the resizing can be done more reliably.

[duezerouno]

Fixes #54. Thank you @Merott

[LoganLehman]

@Merott @patrickmarabeas - Can we please get this merged?

[patrickmarabeas]

Integrated the changes; check v4.2.2 and see whether it works as expected.