Remove Phing and PEAR deps from composer.json, refs T203

Summary:
PEAR deps nearly double the time it takes to `composer update`.
We should be able to create builds using Grunt task instead.

Test Plan: none

Reviewers: rjmackay

Reviewed By: rjmackay

Subscribers: lkamau

Maniphest Tasks: T203

Differential Revision: https://phabricator.ushahidi.com/D71