fix mime-type bug

Default magic_file can't take cognizance of right mime-type.
So I added magic_file option.
update aws.phar

I caught php fatal error.
This is message.

PHP Fatal error:  Uncaught exception
'Guzzle\\Common\\Exception\\RuntimeException' with message '/tmp/guzzle-cacert.pem MD5 mismatch: expected 47961e7ef15667c93cd99be01b51f00a but got 5d108f8ab86afacc6663aafca8604dd3' in phar:///.../wp-content/plugins/staticpress-s3/includes/aws.phar/Guzzle/Http/Client.php:378
Stack trace:
 #0 phar://.../wp-content/plugins/staticpress-s3/includes/aws.phar/Guzzle/Http/Client.php(441): Guzzle\\Http\\Client->preparePharCacert()
 #1 phar://.../wp-content/plugins/staticpress-s3/includes/aws.phar/Guzzle/Http/Client.php(67): Guzzle\\Http\\Client->initSsl()
 #2 phar://.../wp-content/plugins/staticpress-s3/includes/aws.phar/Aws/Common/Client/AbstractClient.php(76): Guzzle\\Http\\Client->__construct('https://s3-ap-n...', Object(Guzzle\\Common\\Collection))
 #3 phar://.../wp-content/plugins/staticpress-s3/includes/aws.phar/Aws/Common/Client/ClientBuilder.php(249): Aws\\Common\\Client\\AbstractClient- in phar://.../wp-content/plugins/staticpress-s3/includes/aws.phar/Guzzle/Http/Client.php on line 378, referer: http://.../wp-admin/admin.php?page=static-press-options

So I update aws.phar from http://pear.amazonwebservices.com/get/aws.phar
Merge pull request #2 from mogmet/fix_mimetype_bug

Fix mimetype bug