ruby: update to 2.1.5

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
ruby-publify: Ignore pid file

If Rails didn't shutdown correctly on previous boot, it give up to startup because .pid file is already exists, which means Rails process is already exists.
Since OSv is single process OS we can always ignore this, so remove it before Rails startup.

Signed-off-by: Takuya ASADA <syuu@cloudius-systems.com>
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>