Fix integration tests

[danielrearden]

The fail method in ava only accepts a String -- if anything else is passed to it, it blows up with a cryptic "The assertion message must be a string" message. This fixes these calls so that if a test actually fails, the error that caused the test to fail is shown rather than the aforementioned message.

This change also adds a reminder to install APOC to the contributing guidelines.

[codecov-io]

Codecov Report

Merging #300 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #300   +/-   ##
=======================================
  Coverage   95.47%   95.47%           
=======================================
  Files          10       10           
  Lines        2345     2345           
=======================================
  Hits         2239     2239           
  Misses        106      106

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[codecov-io]

Codecov Report

Merging #300 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #300   +/-   ##
=======================================
  Coverage   95.47%   95.47%           
=======================================
  Files          10       10           
  Lines        2345     2345           
=======================================
  Hits         2239     2239           
  Misses        106      106

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 90bd912...3d1a90b. Read the comment docs.

[johnymontana]

Thanks, @danielrearden!