subclass IPython.core.display HTML object for more flexibility.

By defining `_repr_*_` functions, IPython will just call these
functions when a non-HTML representation is required.
protected class definition instead of dynamic class definition.
add tests for each returned image type for ipython display
alright, changed editor preferences to auto-include EOF line feeds.

sorry for the delay :)
trying to use more standard testing formats.
Merge pull request #107 from plotly/plotly-goes-static

subclass IPython.core.display HTML object for more flexibility.