Try using the block string literal syntax to ensure all of the environment definitions are definitely strings.  Then, also quote the values.

This is intended to fix the problem where travis kerplodes with:

```
$ export ELIOT=eliot==$(python
/home/travis/build.sh: line 158: unexpected EOF while looking for matching `)'
/home/travis/build.sh: line 283: syntax error: unexpected end of file
```