Add Firefox support

[Daniel Roesler]

Tried the demo on Firefox 40.0 Ubuntu 14.04, and the effect doesn't work.

[Cody Sand]

Same in 42.0a2

[Alexey]

Seems like some FF problem. The final div, that "make" whole table to have scroll have strange top value 2e+7px. While Chrome got 20000000px.

http://stackoverflow.com/questions/28260889/set-large-value-to-divs-height

[Chris Polis]

Thanks for sharing the link! Have this working in FF with 69b45e9 - also had to make the rows slightly shorter to have the demo work w/ 1 million rows in FF because of the max height value(see SO post).

[Alexey]

@cmpolis it's would be nice to post warning about FF behaviour somewhere

[Chris Polis]

Put a note in the Readme: https://github.com/cmpolis/smart-table-scroll#known-limitations