Doc: Generate documentation with Sphinx

HTML documentation should be built with sphinx. This enables easy
integration with Read The Docs [1]. It can also be generated manually by
running:

    make -C docs html

A man page can be generated by running:

    make -C docs man

[1]: http://yamllint.readthedocs.org/

docs/conf.py

@@ -0,0 +1,43 @@
+# -*- coding: utf-8 -*-
+# yamllint documentation build configuration file, created by
+# sphinx-quickstart on Thu Jan 21 21:18:52 2016.
+
+import sys
+import os
+
+sys.path.insert(0, os.path.abspath('..'))  # noqa
+
+from yamllint import __copyright__, APP_NAME, APP_VERSION
+
+# -- General configuration ------------------------------------------------
+
+extensions = [
+    'sphinx.ext.autodoc',
+]
+
+source_suffix = '.rst'
+
+master_doc = 'index'
+
+project = APP_NAME
+copyright = __copyright__
+
+version = APP_VERSION
+release = APP_VERSION
+
+pygments_style = 'sphinx'
+
+# -- Options for HTML output ----------------------------------------------
+
+html_theme = 'default'
+
+htmlhelp_basename = 'yamllintdoc'
+
+# -- Options for manual page output ---------------------------------------
+
+# One entry per manual page. List of tuples
+# (source start file, name, description, authors, manual section).
+man_pages = [
+    ('index', 'yamllint', u'yamllint Documentation',
+     [u'Adrien Vergé'], 1)
+]