[Refactor] Consolidate all API calls into an api-client.js file

[vegetabill]

With webpack support enabled by #94 we can now make our browser JavaScript better.

Please move all fetch calls currently in main.js into a new file called api-client.js.

That way we can consolidate all error handling and if the API call returns a 401 we will need to prompt the user to log back in.

[vegetabill]

Blocked on #77 and #96 so all the API calls are there to move.

[y-martinez]

Hi @vegetabill I know that this issue is blocked but I can work on this issue with the fetch calls already exist