Add offsettTop to offsetHeight for scrollHeader

If you have multiple fixed headers, it’s not enough to calculate the
headerHeight as the height of the sticky header element. We need to add
the offsetTop to compensate for the first sticky header.
Merge pull request #36 from follesoe/master

Add `offsettTop` to `offsetHeigh`t for `scrollHeader`. Allows for multiple fixed headers, or a fixed header that sits slightly below the top of the page.
Updated version number
Redesigned script structure

https://github.com/cferdinandi/kraken/issues/38
Redesigned script structure

https://github.com/cferdinandi/kraken/issues/38
added animateScroll to public methods
Updated documentation
New API exposes additional methods for use in your own scripts.
New API exposes additional methods for use in your own scripts.
Launched version 4
Merge branch 'init-5'
Added Luke Siedle as a contributor
Updated docs
Updated docs
Updated docs
Updated docs
Updated docs
Updated docs
Converted `_defaults` to a literal object
Fixed error for null `toggle` argument in `animateScroll` function.

https://github.com/cferdinandi/smooth-scroll/issues/43