Correctly detect `document.documentElement`.

Before, if the `document.documentElement.scrollTop` or `document.documentElement.scrollTop` was `0`, the condition evaluated to false and the scroll value was fetched from `document.body` instead. This raised a warning in chrome. Now, we first find the available scroll element and then get its scroll value.
fix for makefile so its possible to compile minified version
added uglifycss so we can put this on cdnjs
switched to d3-tip.min.* to be consistent with package name
Merge pull request #46 from deanmalmgren/make-fix

make fix
Merge pull request #41 from surjikal/patch-1

Correctly detect `document.documentElement`.
ensure tooltip is out of document flow on initialization.  Fixes #45
fix #47.  remove old directional classes when running tip.show again
Merge remote-tracking branch 'upstream/master' into amd

Conflicts:
	index.js