Including hub server for integration tests

[th0mas]

Includes the features detailed in #13

[codecov]

Codecov Report

Merging #14 into master will increase coverage by 1.47%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #14      +/-   ##
==========================================
+ Coverage   58.82%   60.29%   +1.47%     
==========================================
  Files          12       12              
  Lines         136      136              
==========================================
+ Hits           80       82       +2     
+ Misses         56       54       -2     

Impacted Files	Coverage Δ
lib/smart_home_firmware/client/hub_client.ex	72.91% <0.00%> (+4.16%)	⬆️

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[nelsonic]

@th0mas hopefully you can use the Heroku version of the Hub/Auth server dwyl/smart-home-auth-server#19 for this. 🤞

[th0mas]

Fixed in an alternative way in dwyl/smart-home-auth-server#14

[nelsonic]

@th0mas a lot of the detail in this PR is not captured anywhere and you spent a decent chunk of time exploring it.
If we ever need to run multiple apps on Travis-CI again, it could be worth having this documented somewhere.
e.g: a run-multiple-apps.md in https://github.com/dwyl/learn-travis 💭