Behat: upgrade for php 7.2

[Rebecca Blundell]

1. Upgrade behat to run in php 7.2

2. Figure out what best to do for this problem:
Currently there is an issue with the Behat2Renderer.php file in the html report. It uses count() as a test whether object properties return null. As in 7.2 passing null to count results in a warning, running tests currently produces a long list of warnings, so we should probably change that.

It looks like implementing Countable on the object may solve this.

Related to https://bugs.launchpad.net/mahara/+bug/1767945

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/8882

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/8882
Committed: https://git.mahara.org/mahara/mahara/commit/584c6aff2e098398631d57591d6bd41ff1f01e88
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 584c6aff2e098398631d57591d6bd41ff1f01e88
Author: Rebecca Blundell <email address hidden>
Date: Wed May 23 15:47:07 2018 +1200

Bug 1772792: Update behat for php7.2

- changed composer dependencies to make 7.2 work
- switched to carat syntax which allows upgrade up to anything below the next major version.
- fixed use of count to check for null in Behat2Renderer.php
- tested dependencies with php 5.6, 7.0, 7.1, 7.2. You do need to
manually delete the composer.lock file and run make initcomposer to resolve issues.

behatnotneeded

Change-Id: I725d8ac6a2f8ca9d67c95d7d6184882a364c0762