Update DeploystrategyAbstract.php

present simple tense correction in exception message
Merge pull request #102 from buric/patch-1

Update DeploystrategyAbstract.php (typo)
use current master-dev branch for phpunit/phpunit-mock-objects

there is a mocking issue in php 5.6 which hopefully soon gets fixed
cleaned up plugin class and divided installer into Installer/CoreInstaller and Installer/ModuleInstaller

removed original Installer
updated tests
refactoring CoreInstaller
moved constant SORT_PRIORITY_KEY to ProjectConfig
changed travis notifications temporarily