Squashed 'subtree/bokehjs/' changes from ddf1bec..4cc464f

4cc464f fixed the legend bug, cleaned up master diff
c2fb0a7  goto http://localhost:5000/test/legend_test?filter=legend_test_overlap to see the legend bug
c91b837  merged
62d5a1b attempt to make lines sharper by rounding pixel coordinates
626bcd1  added memoize library
c4cd225  merged
201ed27  added memoization to ticking and text meauserment functions
bfa47d1 Merge branch 'subtree'
4eacc9e improve ticking on user bound axes when panning/zooming, etc
9e17cd3 Merge branch 'subtree'
770db70 fix axis rule placement errors due to insufficient precision
955dbe3 Merge branch 'subtree'
9ae86c7 revert last commit, re-ticking breaks with panning

git-subtree-dir: subtree/bokehjs
git-subtree-split: 4cc464f4e1eafb109822286084d7c58c2e181418
 updated bokehjs