Update Phile for a potential 1.7.2 release

[Schlaefer]

[TASK|BUGFIX] Update Phile for a potential minor 1.7.2 release

This pull request:

• runs composer update to update underlying libraries
  • fixes #303 by including an updated phile-composer-plugin version
  • fixes some composer update related issues (i.e. addressing some PHPUnit test case failures)
• changes system requirements
  • updates minimum PHP version from 5.4 to 5.6
  • adds PHP 7.0, 7.1, 7.2 testing to Travis-CI
  • removes HHMV testing from Travic-CI

@PhileCMS/Phile please review this pull request

[Frodox]

Woooho