Write new endpoint action generators and middleware

[DanielleHuisman]

Write new action generator which generates action that use humps and Fetch API.

• [x] Fetch API request
• [x] Endpoint action generator
• [x] Redux middleware (see comment below)
• [x] Support async bailout function
• [x] Support async payload parse functions (e.g. the default getJSON from src/util.js)
• [x] Support both entity and custom endpoints
• [x] Support (de)camelize options (using humps)
• [x] Support normalizr

[DanielleHuisman]

With the rewrite one of the plans was to use redux-thunk, however there are multiple reasons to keep it as middleware (the state of v1.x):

• Performance: only one function handles all complicated API requests instead of generating the same function over and over again (e.g. with Redux Thunk or Saga).
• Action history: with Redux Thunk it's difficult/impossible to fully serialize actions and see where certain data comes into play. Middleware helps with this as all data is contained in actions.
• Redux Thunk / Saga is being considered as quite an anti-pattern for multiple reasons (including the one(s) above). A quick search on Google will help you find a better explanation of this topic.

TODO: Re-implement middleware and remove redux-thunk.

P.S. consider using the request action type as middleware "trigger" as this action type is basically pointless and prevents a duplicate application re-renders.