Etcd consul crypt

fixes #14 

This is a WIP - do not merge.

This PR adds support for xordataexchange/crypt in both plain text and encrypted modes.  Inserts etcd/consul configuration in the precedence order as follows:

// flag
// env
// config
// key/value store
// default

Please review and comment before I go further with the implementation.  Made one breaking change to an exported function MarshallReader() to specify the config file to be marshalled so I could reuse the function with the byte array that comes back from etcd/consul.