Fix travis build image in the documentation

Author: ecarreras

docs/index.rst

@@ -6,7 +6,8 @@ LibComXML: Python object XML serialization
 
 Release v\ |version|
 
-.. image:: https://travis-ci.org/gisce/libComXML.png?branch=master   :target: https://travis-ci.org/gisce/libComXML
+.. image:: https://travis-ci.org/gisce/libComXML.png?branch=master
+    :target: https://travis-ci.org/gisce/libComXML
 
 Guide
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