Adding link to actual webpage for tutorial information.

The tutorial1.py directs the user to the tutorial web page, but does
not provide the specific URL.  I have added it.
Merge pull request #262 from amormachine/master

Adding link to actual webpage for tutorial information.
Improving some property definitions
Adding initial Matplotlib Figure conversion to Bokeh, with small example
Renaming the Pattern property to DashPattern, and fixing up its implementation to also take strings and lists of ints
Adding dashes to mplsupport
Small hack to pyplot.py to set 'curplot' in bokeh.plotting. (Needed by show() in some cases)
fix #265
fix #266

Text color is determined by current fill, which the renderers may change
in draw_legend(). Need to reset label_props before every text draw.
print info test does not need to check processor
fix #269

For now, default `text_color` to 'black'. Better solution awaits a style
sheet implementation.
fix #161

This turned out to be two issues:

* all arrays/iterables were assumed to have units = "data"
* circles should only send size or radius in spec, but not both
remove spurious debug print
fix #161

added alpha propertes and line_width as DataSpecs
fix #272
fix #273
fix #274
use warnings.warn for deprecations, not print()
Formatting license.txt with hard line breaks (content unchanged)
fix #270

Issue was data_range1d incorrectly computing max and min of the data
when there were some columns that were nested arrays (patches, etc). Use
_.flatten(), also simplifies code.