Test against PouchDB and PouchDB Server

This is just an example of how you could set up SQLdown to test against PouchDB and PouchDB server, following instructions from [here](https://gist.github.com/nolanlawson/f2f4d7e2e6f426502b94).  The `test-pouchdb-all.sh` script just contains whatever client/server combinations I could think of off the top of my head.

BTW the tests currently fail with:

```
  1) test.replication.js-local-http Test _conflicts key:
     Uncaught TypeError: Cannot read property 'rows' of undefined
      at /Users/nolanlawson/workspace/sqldown/node_modules/pouchdb/tests/test.replication.js:465:18
      at /Users/nolanlawson/workspace/sqldown/node_modules/pouchdb/node_modules/pouchdb-mapreduce/utils.js:29:9
      at process._tickCallback (node.js:419:13)
```