Add an openDelay option

[stevenbenner]

Since PowerTip currently supports a user defined delay before closing tooltips via the closeDelay option it makes sense that it should support a user defined delay before opening tooltips.

There may be additional timing headaches involved in implementing this feature. Investigate what it will take to add an openDelay option to PowerTip and implement it if it makes sense and doesn't add a lot of code to the project.

Originally requested by Dennis Lembrée via tweet.