fix broken axis()/xaxis()/yaxis()
remove 'default' field from python side
DataSpec.to_dict() should return {} in the default case
Merge remote-tracking branch 'origin/master' into task/remove_default

Conflicts:
	bokeh/plotting.py
merge
Merge branch 'task/remove_default' of github.com:ContinuumIO/bokeh into task/remove_default
Merge branch 'master' into task/remove_default
update tests
better indicator for 'not set'
add helpul comment
Merge pull request #1001 from ContinuumIO/task/remove_default

remove "default" from glyph specs