Add some documentation for HITRAN query

Author: Miguel de Val-Borro

astroquery/hitran/__init__.py

@@ -5,4 +5,4 @@
 
 :Author: Adam Ginsburg ([email protected])
 """
-from .reader import download_hitran, read_hitran_file
+from .reader import download_hitran, read_hitran_file, cache_location

docs/hitran/hitran.rst

@@ -0,0 +1,37 @@
+.. doctest-skip-all
+
+************************************
+HITRAN Queries (`astroquery.hitran`)
+************************************
+
+Getting started
+===============
+
+This module provides an interface to the `HITRAN`_ database API.  It can
+download a data file including transitions for a particular molecule in a given
+wavenumber range.  The file is downloaded in the `~hitran.cache_location`
+directory and can be opened with a reader function that returns a table of
+spectral lines including all accessible parameters.
+
+Examples
+========
+
+This will download all transitions of the main isotopologue of water between
+the wavenumbers of 3400 and 4100 cm\ :sup:`-1`\ .
+
+.. code-block:: python
+
+    >>> import os
+    >>> from astroquery.hitran import read_hitran_file, cache_location, download_hitran
+    >>> download_hitran(1, 1, 3400, 4100)
+    >>> tbl = read_hitran_file(os.path.join(cache_location, 'H2O.data'))
+
+Transitions are returned as an `~astropy.table.Table` instance.
+
+Reference/API
+=============
+
+.. automodapi:: astroquery.hitran
+    :no-inheritance-diagram:
+
+.. _HITRAN: http://hitran.org