Added docs

Author: Ankur Chauhan

docs/running-on-mesos.md

@@ -311,6 +311,13 @@ See the [configuration page](configuration.html) for information on Spark config
   <td>Attribute based constraints to be matched against when accepting resource offers.</td>
   <td>
     Attribute based constraints on mesos resource offers. By default, all resource offers will be accepted. Refer to <a href="http://mesos.apache.org/documentation/attributes-resources/">Mesos Attributes & Resources</a> for more information on attributes.
+    <ul>
+      <li>Scalar constraints are matched with "less than equal" semantics i.e. value in the constraint must be less than or equal to the value in the resource offer.</li>
+      <li>Range constraints are matched with "contains" semantics i.e. value in the constraint must be within the resource offer's value.</li>
+      <li>Set constraints are matched with "subset of" semantics i.e. value in the constraint must be a subset of the resource offer's value.</li>
+      <li>Text constraints are metched with "equality" semantics i.e. value in the constraint must be exactly equal to the resource offer's value.</li>
+      <li>In case there is no value present as a part of the constraint any offer with the corresponding attribute will be accepted (without value check).</li>
+    </ul>
   </td>
 </tr>
 </table>