OrderedClassElementsFixer - PHPUnit assert(Pre|Post)Conditions methods support

[meyerbaptiste]

Add support for PHPUnit TestCase::assertPreConditions() and TestCase::assertPostConditions() methods.

TestCase::assertPreConditions() is called between TestCase::setUp() and test.
TestCase::assertPostConditions() is called between test and TestCase::tearDown().

[SpacePossum]

👍
RTM from me if the tests pass

[coveralls]

Coverage increased (+0.0007%) to 92.853% when pulling 153e50c on meyerbaptiste:fix_orderedclasselementsfixer into 07430f5 on FriendsOfPHP:master.

[SpacePossum]

Thank you @meyerbaptiste.