Add Composer,

Todo:
- Error: Execution of '/usr/bin/yum -d 0 -e 0 -y install php-pecl-ssh2'
returned 1: Error: Nothing to do
- Error: Could not update: Execution of '/usr/bin/yum -d 0 -e 0 -y
install mcrypt' returned 1: Error: Nothing to do
- Error: Execution of '/usr/bin/yum -d 0 -e 0 -y install php-oauth'
returned 1: Error: Nothing to do
- Error: Could not start Service[redis]: Execution of '/sbin/service
redis start' returned 1:
- Error: Execution of '/usr/bin/yum -d 0 -e 0 -y install php-pecl-http'
returned 1: Error: Nothing to do
- Error: Execution of '/usr/bin/yum -d 0 -e 0 -y install
php-pecl-gearman' returned 1: Error: Nothing to do
- The following SSH command responded with a non-zero exit status.
Vagrant assumes that this means the command failed!