[Upgrade] Slim 2.2 -> 2.4
[Fixed] .htaccess with correct rewrite rules so it is compatible with "merchant-admin" approach
Merge branch 'master' of https://github.com/ryderlee/php_backend

Conflicts:
	composer.lock
	vendor/autoload.php
	vendor/composer/autoload_real.php
	vendor/slim/slim/index.php