Updates .gitignore

To ignore swap files from getting into repository
currently the implemented ignore is *.swp
however vim adds more swap files if these files exists,
so improving this with *.sw?

Change-Id: Iff581457cabe936b8b285142caff92fcc849f04a
Closes-Bug: #1255876

.gitignore

@@ -6,7 +6,7 @@ subunit.log
 cover
 *.pyc
 .idea
-*.swp
+*.sw?
 *.egg
 *~
 .tox