Update documentation regarding addition of options to panInsideBounds and setMaxBounds. Refs #1879
Merge branch 'gh-pages' of https://github.com/davidjb/Leaflet into gh-pages-master

* 'gh-pages' of https://github.com/davidjb/Leaflet:
  Update documentation regarding addition of options to panInsideBounds and setMaxBounds. Refs #1879
update setMaxBounds description