Move be_normalized_to matcher to Griddler::Testing

This allows adapter gems to take advantage of the matcher.
Remove Postmark adapter

Replace with griddler-postmark gem.

Resolves #129
Remove Cloudmailin adapter

Replace with griddler-cloudmailin gem.

Resolves #126
Remove references to adapter gems in code

* Remove dependency on adapter gems
* Change :sendgrid references to :default for email service and
  configure a fake one rather than referencing
  Griddler::Sendgrid::Adapter
* Stub out a fake "working" adapter for when it matters

Resolves #124
Update body parser regex to allow for new lines

* Add spec for and handle proper parsing of some Gmail responses
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.
better name than @hash
better name than address_hash