Add gitignore file
Fix bugs, update documentation

I fixed two bigs bugs:
1. Hash tag jumping
2. Problem with settings reference when multiple widgets on the same
page

I also finished the documentation with three examples.  I added sections
for dependencies, and discussed how the widget is different from other
plugins.  I filled in a few important details hear and there.

Besides these items I refactored the code to make some of the variable
and function names clearer; I changed how I declared functions to make
it clearer and how I used the $.data() function.