Add dnest4 to the test Docker containers

This adds DNest4 to the test Docker containers.

It also updated how PolyChord is installed in the containers due to updates to that packages installation - see #497 (closed).

cc @andrew.kim @christopher-berry

containers/Dockerfile-test-suite-python27

@@ -41,7 +41,7 @@ coverage-badge
 RUN pip install corner lalsuite astropy gwpy theano
 
 # Install samplers
-RUN pip install cpnest dynesty emcee nestle ptemcee pymc3 pymultinest kombine ultranest
+RUN pip install cpnest dynesty emcee nestle ptemcee pymc3 pymultinest kombine ultranest dnest4
 
 # Install pymultinest requirements
 RUN apt-get install -y libblas3 libblas-dev liblapack3 liblapack-dev \
@@ -55,7 +55,7 @@ ENV LD_LIBRARY_PATH $HOME/MultiNest/MultiNest_v3.11_CMake/multinest/lib:
 
 # Install Polychord
 RUN git clone https://github.com/PolyChord/PolyChordLite.git \
-&& (cd PolyChordLite && make pypolychord  MPI= && python setup.py install)
+&& (cd PolyChordLite && python setup.py --no-mpi install)
 
 # Install PTMCMCSampler
 RUN git clone https://github.com/jellis18/PTMCMCSampler.git \