Tests fail if PELIAS_CONFIG environment variable is set

[orangejulius]

I set PELIAS_CONFIG in my .bashrc file so that pelias.json does not clutter up my home directory. However, I have to unset that variable in order for the tests to pass.

[missinglink]

see setup() and teardown() functions here for an example of how to avoid this issue.

It might be best to create a more formal way of enforcing the default config during testing across all our repos.

[orangejulius]

We've started using proxyquire in some places with relatively good results. I like that it completely removes any dependency on the actual pelias-config code, the filesystem, and env vars