Use waitress on Heroku

Replace use of gunicorn with waitress when deploying to Heroku. Update
external dependencies.
Refactor responsibility to random word choice

Move control of random word choice from view to wordnet module. Random
number sequence and filter functions can optionally be passed to wordnet
functions.
Create packages for views and models

Group views and models for application in sub-packages beneath the
application package.
Enable sub-domain support

Enable serving different APIs from different sub-domains. Currently only
the TwoSlug sub-domain is supported.
Default template is for TwoSlug

Rename the default, or index, template to reflect it's use for the
TwoSlug endpoint.
Use relative imports when appropriate

Relate imports are used when referencing modules within the TwoSlug
application
Dynamicly generate banner URL

Determine the banner URL from the banner name.
Named endpoints to TwoSlug applications

Use namespaced Flask endpoints for all endpoint functions used by the
TwoSlug application.
Flask application for DogePoet

Create a DoePoet application on a new subdomain that generates random
Doge poetry from the WordNet database.