Adds Python-PouchDB as an external project

Like PouchDroid, but for another dev environment. Disclaimer: my project, so I'm biased. Feel free to alter description/not add it.
(#2206) - Replace goodfirstpatch with help wanted
(#2185) - Add ie to allowed failures
(#2185) - Fix typo in travis.yml file
(#1131) - Document expected _local 404 thrown
(#1622) - test in phantomjs

Also add the ability to specify whether or
not to use the ES5 shims, since phantomjs
needs them.
(#2193) - deprecate latest for now
(#2214) - upgrade browserify and mkdirp