[#7995] share python env in /allura-data not in local dir

This is so it won't be shared to host machine if using docker-machine (e.g. Mac/Win
using Docker Toolbox).  No point in sharing there since the environment has
different system libs linked and can't be re-used.

Also fixes a warning about relative paths.
diff --git a/Allura/docs/getting_started/installation.rst b/Allura/docs/getting_started/installation.rst
index 203d6f5..029e21a 100644
--- a/Allura/docs/getting_started/installation.rst
+++ b/Allura/docs/getting_started/installation.rst
@@ -244,12 +244,14 @@
 
 These are created on first run.
 
-Current directory mounted as :file:`/allura` inside containers.
+Current directory mounted as :file:`/allura` inside containers.  This means your current source code in your host
+environment is shared with the containers.  You can edit Allura code directly, and the containers will reflect your
+changes.
 
 Python environment:
 
-- :file:`env-docker/python`
-- :file:`env-docker/bin`
+- :file:`/allura-data/env-docker/python`
+- :file:`/allura-data/env-docker/bin`
 
 Services data:
 
diff --git a/docker-compose.yml b/docker-compose.yml
index 155a421..6822677 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -24,8 +24,8 @@
   volumes:
     - .:/allura
     # mount env to allow update and sharing with taskd container
-    - env-docker/python:/usr/local/lib/python2.7
-    - env-docker/bin:/usr/local/bin
+    - /allura-data/env-docker/python:/usr/local/lib/python2.7
+    - /allura-data/env-docker/bin:/usr/local/bin
     # mounting it separatelly to create git, svn, hg directories automatically
     - /allura-data/scm/git:/allura-data/scm/git
     - /allura-data/scm/hg:/allura-data/scm/hg