fix(web-server): #581 HTTPS Support for Karma Proxy

Add config.protocol = 'http' or 'https' to indicate running Karma server in
http or https mode (to ensure secure cookies are handled properly from the
proxied urls).

Add config.cert { key: 'file_name', cert: 'file_name' } to identify the .pem
files to use for the server certificate.

This fix requires node-http-proxy from https://github.com/jayv/node-http-proxy
as this is the only http-proxy implementation that properly supports rewriting
the Location headers.

Closes #581
fix(web-server): #581 HTTPS Support for Karma Server

Add 'pem' dependency to allow for creating one-time certificates
when config.cert.key/cert are not specified.

Cleanup of some lint errors (oops)

Closes #581
fix(web-server): #581 HTTPS Support for Karma Server

Better default for config.cert

Closes #581