Generate 10 minutes to Koalas as documentation (databricks#853)

This PR adds our "10 minutes to Koalas" into official documentation. This [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/HyukjinKwon/koalas/generate-10min-page?filepath=docs%2Fsource%2Fgetting_started%2F10min.ipynb) has the changes made in this PR.

1. In notebook, `...` and `>>>` are removed now. I initially wanted to use `pandoc` right away but it couldn't the output properly. Instead, I used `nbsphinx` that uses `nbconvert` which uses `pandoc`. With `nbsphinx`, `...` and `>>>` are rendered properly (with `ipython` directive).

2. Sphinx extension `IPython.sphinxext.ipython_console_highlighting` and `ipython` dependency were added in order to recognise `ipython3` directive with reStructuredText files and Sphinx.

3. Added the link to Jupyter notebook (Binder) to the tutorial itself.

README.md

@@ -10,7 +10,7 @@ pandas is the de facto standard (single-node) DataFrame implementation in Python
 
 This project is currently in beta and is rapidly evolving, with a weekly release cadence. We would love to have you try it and give us feedback, through our [mailing lists](https://groups.google.com/forum/#!forum/koalas-dev) or [GitHub issues](https://github.com/databricks/koalas/issues).
 
-Try the Koalas 10 minutes tutorial on a live notebook in Jupyter here [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/databricks/koalas/master?filepath=docs%2F10-minutes-to-Koalas.ipynb)
+Try the Koalas 10 minutes tutorial on a live notebook in Jupyter here [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/databricks/koalas/master?filepath=docs%2Fsource%2Fgetting_started%2F10min.ipynb)
 . The initial launch can take up to several minutes.
 
 [![Build Status](https://travis-ci.com/databricks/koalas.svg?token=Rzzgd1itxsPZRuhKGnhD&branch=master)](https://travis-ci.com/databricks/koalas)

docs/source/conf.py

@@ -54,7 +54,9 @@ def gendoc():
     'sphinx.ext.autodoc',
     'sphinx.ext.viewcode',
     'numpydoc',  # handle NumPy documentation formatted docstrings. Needs to install
-    'nbsphinx',  # Jupyter Notebook. Needs to install
+    'nbsphinx',  # Converts Jupyter Notebook to reStructuredText files for Sphinx.
+    # For ipython directive in reStructuredText files.
+    'IPython.sphinxext.ipython_console_highlighting',
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -63,7 +65,7 @@ def gendoc():
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 # This pattern also affects html_static_path and html_extra_path.
-exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store', '**.ipynb_checkpoints']
 
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'