Use PharData class to extract tarball

In some environments (read: mine), tar binary cannot access temp file because it is locked by php. This will resolve that issue.
Fixes PharData extraction bugs

* $temp gets '.tar.gz' extension
* _extract() method is created
* PharData uses workaround for '--strip-components' compatibility
Makes extraction routine more readable / Fixes overwrite routine

* creates separate _move_overwrite_files() method
* more accurately simulates --strip-components=1 by using $phar->getFileName()
Fixes readability

* two lines were indented with spaces, converted to tabs
Merge pull request #838 into master

Use PharData class to extract tarball