Merge pull request wp-cli#21 from wp-cli/conditional-path

Only attempt to build relative path when inside of Phar

Merge pull request wp-cli#17 from wp-cli/fix-dev-master-conflict

Fix conflict between dev-master and pull-request branches

Merge pull request wp-cli#16 from wp-cli/danielbachhuber-patch-1

Permit 1.x-dev as `dev-master`

Merge pull request wp-cli#15 from wp-cli/13-extract-router

Properly extract router.php from the Phar build

Run system check on `before_invoke`