Add jstree 3.0.0-beta9 to dependencies
Clean up .gitignore in bokeh and bokehjs

Just a bit, use prefix forward slash to minimize impact
of certain rules, e.g. /dist will match only top-level
dist created by setup.py, not parts of bokehjs/src/vendor.
Change base to @base() in has_properties.coffee
Preliminary implementation of ObjectExplorerView
Allow to configure where redis files are stored
Remove CDXPlotContext
ObjectExplorer actually works and renders colorful trees
Make ObjectExplorer.onEvent's debounce configurable
Make context menu depend on node type
Don't show ObjectExplorer's toolbar by default
Add ObjectExplorerTool
Fix require()'s deficiencies and special-case common/base
Limit arrays' items to 100 by default (configurable)
Fix html of PreviewSaveTool's modal
Concat jstree styles to bokeh's styles (set themeUrl to null)
Add ObjectExplorerTool to glyphs/line.py example
Add jstree's styles overrides to avoid external images
Merge branch 'master' into object-explorer
Add PersistentSession abstract class

This is needed to add common raw_js_snippets member. This
should be, however, better organized in future.
Add concat:vendor -> css/bokeh-vendor.css and use it in HTMLFileSession