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/quickstart.rst

@@ -0,0 +1,77 @@
+Quickstart
+==========
+
+Installing yamllint
+-------------------
+
+First, install yamllint. The easiest way is to use pip, the Python package
+manager:
+
+::
+
+ sudo pip install yamllint
+
+If you prefer installing from source, you can run, from the source directory:
+
+::
+
+ python setup.py sdist
+ sudo pip install dist/yamllint-*.tar.gz
+
+Running yamllint
+----------------
+
+Basic usage:
+
+::
+
+ yamllint file.yml other-file.yaml
+
+You can also lint all YAML files in a whole directory:
+
+::
+
+ yamllint .
+
+The output will look like (colors are not displayed here [#colored-output]_):
+
+::
+
+ file.yml
+   6:2       warning  missing starting space in comment  (comments)
+   57:1      error    trailing spaces  (trailing-spaces)
+   60:3      error    wrong indentation: expected 4 but found 2  (indentation)
+
+ other-file.yml
+   1:1       warning  missing document start "---"  (document-start)
+   9:81      error    line too long (84 > 80 characters)  (line-length)
+   31:1      error    too many blank lines (4 > 2)  (empty-lines)
+   37:12     error    too many spaces inside braces  (braces)
+
+Add the ``-f parsable`` arguments if you need an output format parsable by a
+machine (for instance for :doc:`syntax highlighting in text editors
+<text_editors>`). The output will then look like:
+
+::
+
+ file.yml:6:2: [warning] missing starting space in comment (comments)
+ file.yml:57:1: [error] trailing spaces (trailing-spaces)
+ file.yml:60:3: [error] wrong indentation: expected 4 but found 2 (indentation)
+
+If you have a custom linting configuration file (see :doc:`how to configure
+yamllint <configuration>`), it can be passed to yamllint using the ``-c``
+option:
+
+::
+
+ yamllint -c ~/myconfig file.yml
+
+.. note::
+
+   If you have a ``.yamllint`` file in your working directory, it will be
+   automatically loaded as configuration by yamllint.
+
+.. rubric:: Footnotes
+
+.. [#colored-output] The default output format is colored and inspired by
+   `eslint <http://eslint.org/>`_, a great linting tool for Javascript.