Merge pull request #492 from jhlegarreta/doc/change-title-citation-page

DOC: Change title to citation page to make it stand out more

Author: jhlegarreta

docs/citation.rst

@@ -1,5 +1,5 @@
-Citation
-========
+How to cite
+===========
 
 If you use NiFreeze in your research, please cite it using the below
 references as appropriate: