Bump less to @<3.0 so setup.py css works

Dockerfile

@@ -41,7 +41,7 b' RUN apt-get update && apt-get install -y -q \\'
     npm
 
 # In order to build from source, need less
-RUN npm install -g less@1.7.5
+RUN npm install -g 'less@<3.0'
 
 RUN pip install invoke