Revert "Add .check() method"

This reverts commit f72c1257647036a159ccbe64a944a5574586c5cc.

There's no need for a .check() method. If you are generating images from
JavaScript, make sure you use in-viewport when the image is in the dom
only.

Conflicts:
	in-viewport.js
Put in-viewport script tag in head for tests

+ Always use "doc.body", if you store a reference to it, you might end
up with "null" value when the in-viewport <script> tag is placed in
<head>
Check for innerXXX before clientXXX

innerWidth/Height is the correct way to get the viewport.

On IE6/7/8 it does not work so we take the clientWidth/Height.

It seems that getting the viewport correctly on safari mobile is a
complete mess, not yet handled.
new test case: scrolling near the element
remove unecessary code from test page
Precise instructions on quirksmode
remove images references
refactor init
add instructions on dynamic nodes
remove image references
Revert "Check for innerXXX before clientXXX"

document.documentElement.clientHeight seems the most reliable solution
because it removes the scrollbars from the viewport as expected,
window.innerHeight do not.

This reverts commit ea3d771070a6c3f4882637d848094515c9bea346.
0.3.0