Pin version of neuromllite for py3.6

Author: pgleeson

Dockerfile

@@ -76,6 +76,8 @@ RUN sudo pip install neuron==7.8.1
 # See https://github.com/openworm/OpenWorm/pull/316
 RUN sudo pip install 'gitpython==2.1.15' markupsafe
 
+RUN sudo pip install 'NeuroMLlite<0.5.0' # for python 3.6...
+
 RUN git clone https://github.com/openworm/c302.git && \
   cd c302 && \
   git checkout ow-0.9.2 && \