Remove configuration for to, from, and cc

Remove all configuration of addresses

Previously users could configure the format in which they would receive
addresses in to, from, and cc fields of Griddler::Email objects. The
options were :token, :full, :email, :name, or :hash, which was a hash of
all other options.

Configuring :token was previously deprecated, and :hash has been the
default for :from and :cc for a while now. All of these values are
pretty easy to get back with Hash#[], so we're simply removing the
configuration logic and always returning the hash, which is the most
generally useful option.

Could we at least give `@hash` a meaningful name? `@default_config`, `@email_headers`, `@test_values` or something along those lines? I'm still not sure what `@hash` is.