Add call count to profile data.
Get text showing up on the links.

Get the text displaying and positioning correctly. Having the call
counts visible can help find slow functions that also get called too
frequently.
Fix rendering of text and call/calls.
Improve callgraph popover.

Make the title look nicer. Add information on what % value is.
Make the popover better positioned for smaller nodes.
Work on making the layout a bit nicer.
Update tests for Profile::getCallgraph()
Make small circles a min of 4px.

Any smaller and they are really hard to click on.
Use some trigonometry to position line endings better.

Use the target & source data combined with the radius of the circle to
determine the amount of adjustment required to position the end of the
line at the edge of the circle. Doing this adjustment lets the arrow
heads display even on larger circles.

Given the radius of the circle is constant, we can use the angle,
run and trigonometric ratios to determine the dimensions of
a triangle that has radius == hypotenuse.
Fix and expand comments.
Merge pull request #77 from preinheimer/callgraph-call-counts

Callgraph improvements

Fixes #76