The IPython formatters use special methods to compute the format
of objects. These special methods have names like "__html__", but
with this commit these have been changed to "_repr_html_".
pylab tools in getfigs.
* Throughout the codebase, __pretty__ has been changed to
_repr_pretty_ to match general convention for special method
* The logic in pretty.py now matches that in formatters.py in that
formatters that are callables are tried first and then special
methods are used.
* PNG base64 encoding is now done at the ZMQ level, not in the
display formatter itself.
* All formatters are documented as to the exact nature of their
return value. PNGs are not base64 encoded, LaTeX must include
* Updated the Circle display example in docs/examples/core.
* Renamed the sympy printing extension to sympyprinting.py.