Docker Updates (#308)

* new path for python build

* add flag

* build tar using git archive

* no exit from start_ray.sh

* update Docker instructions

* update build docker script

* add git revision

* fix typo

* bug fixes and clarifications

* mend

* add objectmanager ports to docker instructions

* rewording

* Small updates to documentation.

docker/deploy/Dockerfile

@@ -3,6 +3,8 @@
 
 FROM ray-project/base-deps
 ADD ray.tar /ray
-WORKDIR /ray/lib/python
+ADD git-rev /ray/git-rev
+WORKDIR /ray/python
 RUN python setup.py install
 WORKDIR /ray
+RUN echo "tail -f /dev/null" >> scripts/start_ray.sh