Option to disable SSL certificate verification

[ea167]

Hello,

First of all, congrats for this great Kibana proxy, it helps a lot!

When trying to use aws-es-kibana on a laptop connecting to AWS Kibana through an SSH tunnel, we get an [ERR_TLS_CERT_ALTNAME_INVALID] error due to http-proxy.

However there is an option on line 129 of index.js that is hardcoded to secure: true that would allow the use case to work.

Would it be possible to have a command-line argument to put this option as false?

[ea167]

PR #63 to add the -U (unsecure, to disable SSL certificate validation) option