Browser compatibility: make swagger-client not dependent on fs

fs is currently called in the swagger client constructor:
https://github.com/godaddy/kubernetes-client/blob/master/lib/swagger-client.js#L106

This causes errors in browser and makes it very difficult to construct a browser-friendly swagger client.

Start at lib/swagger-client.js around line 106, where fs is called in the swagger client constructor. Trace why that dependency is loaded during construction and check the browser-facing construction path. Done means a browser can construct the swagger client without errors caused by fs.

Written by the indexing model from the issue text.