Update test suite to work with 0.17

[eeue56]

Problem:

• core tests didn't work with 0.17

Solution:

• Use updated elm-test
• Update syntax
• to run now, you just need to do ./set-up-tests.sh and it will take care of everything
• Update travis (currently failing due to Json.Decode possible bug, see other notes)

Other notes:

• No longer need to clone elm-console or anything else! No need for any external native packages
• Every test passed, except for decoding large ints in Json.Decode. Based on this commit, it might just be that the tests are outdated, and should actually be failing for ints like 1801439850948 anyway. Updating the tests to expect decoding to fail means the whole test suite passes.
• When 0.17 is released, I'll make a PR to use 0.17 final binary and update elm-test package to be elm-community/elm-test

[evancz]

Awesome, thank you!

[evancz]

Awesome, thank you!