Fixes issue 592
Replaced tabs with spaces
Added support for mixed list in tools. Modified an example for proof of concept
Replaced tabs by spaces..
Merge branch 'master' of https://github.com/tarzzz/bokeh into issue-592

Conflicts:
	bokeh/plotting_helpers.py
Merge branch 'master' of https://github.com/ContinuumIO/bokeh into issue-592
Removed vertical space, added exception handling
Replaced str with string_types
Issue warning if a certain tool is repeated in the tools list
Using __name__ instead of __str__ attribute
Added identity of repeated tools in warning
Added list instead of str object.
Merge pull request #654 from tarzzz/issue-592

Fixes issue 592