add Gaia to the module list [skip ci]
@@ -109,6 +109,7 @@ List of Modules
* `Open Expolanet Catalog (OEC) <http://astroquery.readthedocs.io/en/latest/open_exoplanet_catalogue/open_exoplanet_catalogue.html>`_
* `JPL Horizons <http://astroquery.readthedocs.io/en/latest/jplhorizons/jplhorizons.html>`_: JPL Solar System Dynamics Horizons Service
* `OAC API <http://astroquery.readthedocs.io/en/latest/oac/oac.html>`_: Open Astronomy Catalog REST API Service
+ * `Gaia <http://astroquery.readthedocs.io/en/latest/gaia/gaia.html>`_: European Space Agency Gaia Archive
Additional Links
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