PressStart event and fixes.

Class initialization with default values.
New event for PressStart.
Documentation improvements.

Added callback functions with parameters

Now it is possible to register a callback function that has an extra parameter that provides a pointer to some data relevant for the callback.

universal input enabled.

Now it is possible to use other sources of input, not just digital pins.
Some fixes.
Deactivating internal pullup is now possible.

Debouncing improved.

some improvements regaring the debouncing and enabling setting the timer where bounces are accepted.

Stable

Stable version of the OneButton now in Arduino Library format.