ref(builder): remove python and jq from the builder script

Went ahead and rebased #2155. This fixes up a lot of the parsing issues we're seeing with `jq` and `python` in the builder script. We've outgrown the use cases of these tools for parsing JSON objects.

```
><> deis config:set NEWRELIC_APP_NAME="Project Staging AWS"
Creating config... done, v2

=== go
NEWRELIC_APP_NAME: Project Staging AWS
><> git push deis master
[...]
Removing intermediate container 9ebeb3c4fca0
Step 4 : ADD slug.tgz /app
 ---> 02e091f27d81
Removing intermediate container 0a143dbe21d1
Step 5 : ENV GIT_SHA 060da68f654e75fac06dbedd1995d5f8ad9084db
 ---> Running in 2a32dcbd7a10
 ---> bb91eaad5888
Removing intermediate container 2a32dcbd7a10
Successfully built bb91eaad5888
-----> Pushing image to private registry

-----> Launching...
       done, go:v3 deployed to Deis

       http://go.fishworks.io

       To learn more, use `deis help` or visit http://deis.io

To ssh://git@deis.fishworks.io:2222/go.git
 * [new branch]      master -> master
```

fixes #2343 
fixes #2477
This line should come after the next error-handling block. It might be problematic or at least wasteful to create a new `Reader` if there was an error.