Squashed 'subtree/bokehjs/' changes from b8ea8f7..ddf1bec

ddf1bec revert last commit, re-ticking behaves very badly with panning
64979e4 axes with user bounds should re-tick as necessary when zoomed in and out or panned
bf60727 Merge branch 'master' of github.com:ContinuumIO/Bokeh
e45b7f7 Merge branch 'master' of github.com:ContinuumIO/Bokeh

git-subtree-dir: subtree/bokehjs
git-subtree-split: ddf1bec895f7f5587ef155f0af41a831629e5400
Merge commit 'bdad8f8531a0afb9fd70e4b63944d25b6482b096'