add new extension path

Signed-off-by: Ahmad Shah Hafizan Hamidin <ahmadshahhafizan@gmail.com>
refactor service provider

Signed-off-by: Ahmad Shah Hafizan Hamidin <ahmadshahhafizan@gmail.com>
Merge pull request #43 from ahmadshah/feature/extension

Add new extension path to match Laravel 4.3