Update to phoenix 1.6 issue #61 [Part 2]

[nelsonic]

Building on the work done by @ajmeese7 in #61 ("Part 1") to update to this tutorial/repo to Phoenix 1.6,
this PR:

• removes the files we no longer need and updates the templates to use /assets/ directory.

Follows the instructions in Chris McCord's guide #55 (comment)
Aaron had already done most of the work to upgrade. 🙌
This tidy up was only required for anyone who had the older version of the project on their localhost. 🙄

[nelsonic]

Note: Travis-CI is temporarily suspended, see: #55 (comment) related to: dwyl/learn-travis#67
But the tests all pass and the app works on localhost: #55 (comment)

Thanks for reviewing/merging. 👍

[ajmeese7]

LGTM 👍🏻 only exception is that I am getting the following error in my logs, and the image isn't loading in:

[debug] ** (Phoenix.Router.NoRouteError) no route found for GET /images/phoenix.png (ChatWeb.Router)

All the tests pass and the message functionality works though, so something may have just gone wrong in my environment. If you think the problem is localized I'm good to merge, for now I am going to approve of the PR.

[SimonLab]

Looks good to me 👍
I don't have any log errors on my side.
@ajmeese7 maybe you can try to rebuild the app to see if it fixes the log on your side?

[nelsonic]

@ajmeese7 you may need to run mix assets.deploy 💭

[ajmeese7]

@SimonLab rebuilding the app worked, thank you for the suggestion!

Another great PR @nelsonic 🎉