Fix graphs created in not-displayed divs.

This distinguishes two cases:

- graphs with explicit height/width in graph options. They should
  be drawn correctly after display, no resize needed.

- graphs without explicit height/width are supposed to inherit
  the size from the surrounding div. They needs a .resize()
  call after display.

Tests are included for both.

Fixes issue 238.
Merge pull request #259 from klausw-g/resize-fix

Fix graphs created in not-displayed divs.
Only resize canvas if the size changed.

Resizing the canvas erases it, and Dygraphs had skipped the redraw
when it thought it wasn't necessary, leading to blank graphs after
a redundant .resize() call.
Merge pull request #260 from klausw-g/resize-fix-2

Only resize canvas if the size changed.
Add comment to resize test case as a follow on to pull request 260.
Add comment to resize test case as a follow on to pull request 260.
Merge branch 'master' of https://github.com/danvk/dygraphs
BUGFIX: Fixed Bug created by extracting different rows for each series (to fix the big not connecting lines at edges). Now all calls to the getLeftBoundry method are done with the correct set index resulting in a correct behaviour now.
Merge branch 'left-boundry-fix' into sauter-dygraphs-development