refactor default options merge to avert side effects.

[jonstorer]

setting options this way:

$.extend(defaults, options);

will overwrite the default variable with the param options.

For example, If there are two endless scrolls on the page, the 2nd endless scroll could receive 'dirty' defaults from the first call.

This:

$.extend({}, defaults, options);

won't do that. It keeps defaults clean and separate from the intended options.

[fredwu]

Merged and tagged a new release! Thanks! :)

[jonstorer]

welcome!