Update the singularity build script

Build from source ubuntu distribution.

singularity/Singularity.0.3.3

-Bootstrap: docker
-From: bilbydev/test-suite-py3
+Bootstrap: debootstrap
+OSVersion: bionic
+MirrorURL: http://us.archive.ubuntu.com/ubuntu/
 
 %help
-A singularity container for running bilby scripts
+A singularity container for running bilby scripts. Built from Ubuntu 18.04,
+this contains all the software to run bilby. Available samplers are "dynesty"
+and "nestle". Other samplers will be added in the future.
 
 %post
-export PATH=/opt/conda/bin:${PATH}
+apt-get update && apt-get install -y --no-install-recommends apt-utils
+apt-get install -y curl
+apt-get install -y gcc
+apt-get install -y libgl1-mesa-glx
+apt-get install -y libdpkg-perl
+apt-get install -y python3
+apt-get install -y python3-dev
+apt-get install -y python3-distutils
+curl -sS https://bootstrap.pypa.io/get-pip.py | python3
+pip install --upgrade pip
+pip install future
+pip install corner
+pip install numpy>=1.9
+pip install matplotlib>=2.0
+pip install scipy>=0.16
+pip install pandas
+pip install deepdish
+pip install mock
+pip install dynesty
+pip install nestle
+pip install astropy
+pip install lalsuite
+pip install urllib3
+pip install gwpy
 pip install bilby==0.3.3
-
-%environment
-LD_LIBRARY_PATH=/MultiNest/lib
-export LD_LIBRARY_PATH