Fix the build, missing quote made $PACKAGES=''

Author: vdboor

.travis.yml

@@ -7,7 +7,7 @@ python:
 env:
 - PACKAGES="django>=1.5.0,<1.6.0 django-mptt<0.7.0"
 - PACKAGES="django>=1.6.0,<1.7.0 django-mptt<0.8.0"
-- PACKAGES="django>=1.7.0,<1.8.0 django-mptt<0.8.0
+- PACKAGES="django>=1.7.0,<1.8.0 django-mptt<0.8.0"
 - PACKAGES="django>=1.8.0,<1.9.0"
 - PACKAGES="django>=1.9.0,<1.10.0"
 matrix: