Add sphinxify_mimebundle function for sending docstrings as text+HTML

"mimebundle" as understood by Jupyter.

The name and location of this code are debatable, as this is very
specifically for use with Jupyter.  For the text format we use
sage.misc.sagedoc.format which is similar to what sage_getdoc does.
Here we assume that we are being passed the original docstrings
unmodified (otherwise sphinxify won't do anything interesting).

src/sage/misc/sphinxify.py

@@ -26,6 +26,9 @@
 import re
 import shutil
 from tempfile import mkdtemp
+
+import six
+
 from sphinx.application import Sphinx
 
 
@@ -166,6 +169,54 @@ def sphinxify(docstring, format='html', strip_math_delims=True):
     return output
 
 
+def sphinxify_mimebundle(docstring):
+    r"""
+    Like `sphinxify`, but returns a Jupyter "mimebundle": a dict whose keys are
+    MIME types and the values are the representation of the docstring in each
+    type.
+
+    This returns the ``text/plain`` docstring as passed through
+    ``sage.misc.sagedoc.format`` which is effectively equivalent to what
+    `sage_getdoc` already returns.  It returns the HTML "sphinxified" docstring
+    with the ``text/html`` MIME type.
+
+    For the HTML output it also converts it to unicode, if it isn't already, as
+    IPython tries to append it to other unicode strings.  It also uses the
+    ``strip_math_delims=False`` option, which is needed for the math to render
+    in the Jupyter Notebook.
+
+    INPUT:
+
+    - ``docstring`` -- string -- a ReST-formatted docstring
+
+    OUTPUT:
+
+    - dict -- keys ``'text/plain'`` containing the plain-text representation fo
+      the docstring, and ``'text/html'`` containing the HTML-rendered
+      representation
+
+    EXAMPLE:
+
+        sage: from sage.misc.sphinxify import sphinxify_mimebundle
+        sage: bundle = sphinxify_mimebundle(':math:`x=y`')
+        sage: bundle['text/plain']
+        'x=y\n'
+        sage: bundle['text/html']
+        u'<div class="docstring">\n    \n  <p><span class="math notranslate nohighlight">\\(x=y\\)</span></p>\n\n\n</div>'
+    """
+    from sage.misc.sagedoc import format
+
+    html = sphinxify(format(docstring, embedded=True), strip_math_delims=False)
+    if not isinstance(html, six.text_type):
+        html = html.decode('utf-8')
+
+    html += (u'\n<script type="text/javascript">'
+             u'MathJax.Hub.Queue(["Typeset", MathJax.Hub, "pager-contents"])'
+             u'</script>')
+
+    return {'text/plain': format(docstring),'text/html': html}
+
+
 if __name__ == '__main__':
     import sys
     if len(sys.argv) == 2: