Add Perl Support

Example:

Adding this line to my `nginx.conf` file does not produce an error:

```
perl_set  $rnd 'sub { return int(rand(10 - 5)) + 5; }';
```

Size before:
```
$ docker images
REPOSITORY           TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
nginx                latest              bc32c7487f40        23 minutes ago      444.1 MB
```

Size after:
```
$ docker images
REPOSITORY           TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
nginx                latest              32293f4d9c89        19 seconds ago      458.4 MB
```

Fixes #1