Make 'matplotlib' optional when using the ipython directive.
Add `ipython_execlines` option to IPython directive.
Update module docstring for IPython directive.
Fix bug where exec_lines was ignored within ipython directive.
Add 'float' option to @doctest pseudo-decorator.
Clean up handling of default values for ipython_mplbackend, ipython_execlines.

When specified as `None` in conf.py, this is treated the same as if not
specified in conf.py at all.
Simplify ipython_directive backend specification.
Place customized doctests in a separate module.
Provide helpful error messages on doctest failures.
Default backend is 'agg'. `None` is no matplotlib.
Minor docstring adjustment.
Docstring update for Sphinx IPython directive.
Set prompt_manager.width to zero for each new document to prevent misaligned Out prompts
Merge pull request #1 from jorisvandenbossche/patch-1

Set prompt_manager.width to zero for each new document to prevent misaligned Out prompts
Docstring updates.
Hold the execution count for @suppress'd inputs.
Merge pull request #4570 from chebee7i/ipydirective

Update IPython directive