Make the zoom slider's zoomLevel=1
position centered.
Do not fire the zoom slider's onChange
event when programmatically setting the
slider position.
Merge pull request #441 from adityab/center-slider

Normalize zoom slider's position for the zoom range
Add test for frame position.
Add a helper function to get the bounding rectangle for an ODF page.
Improve positioning of frame that relative to page.
Add type that is a union of ClientRect and a struct with the same members.
This makes is possible to use them interchangeably.
In older browsers, positioning is only allowed on whole pixels.
The positioning test should set the allowed error higher in such browsers.
Add more supported length units.
And add a bit of documentation.
Check for null return value for getBoundingClientRect.
Slight clarification of exception.