Merge pull request #188 from kobotoolbox/pyxform-upgrade-0.12

Update pyxform to v0.12

Author: jnm

requirements.txt

@@ -4,6 +4,6 @@ jsonschema==2.6.0
 lxml==4.2.1
 path.py==11.0.1
 pyquery==1.4.0
-pyxform==0.11.5
+pyxform==0.12.0
 statistics==1.0.3.5
 XlsxWriter==1.0.4