Change HTML:CSS split view ratio to 70%-30%.

IMO, the HTML DOM is more important than the CSS, so change the height ratio from 50%-50% to 70%-30%.
Fix minor bugs, add comments
Vertical layout in the Sources panel too!

The default 3-column layout in the Sources panel makes it unusable when DevTools is docked vertically; reorganize it with the middle (code) column at the top, and the other two (navigator and debugger) at the bottom, with a 70%-30% height ratio.

Tested quite thoroughly, so everything should be bug-free now.
Update README: instructions on how to dock vertically.

The "Dock Vertically" button is very difficult to find, so that should also be explained in the README.
Merge pull request #3 from vickychijwani/master

Vertical layout in Sources panel, minor enhancements, and bug-fixes.