Panic if set message length as negative

[mkorolyov]

panic: runtime error: makeslice: len out of range

goroutine 12 [running]:
panic(0x1810a0, 0xc82000a7a0)
/usr/local/Cellar/go/1.6/libexec/src/runtime/panic.go:464 +0x3e6
github.com/mkabischev/lodge/ioutil.Read(0x3756b0, 0xc8200645a0, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0)
/Users/mk/work/juno/src/github.com/mkabischev/lodge/ioutil/io.go:9 +0x71
github.com/mkabischev/lodge/server.(*request).data(0xc820016b70, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0)
/Users/mk/work/juno/src/github.com/mkabischev/lodge/server/request.go:49 +0x73
github.com/mkabischev/lodge/server.setCommand.process(0xc820016b70, 0x3743e0, 0xc820016570, 0x0, 0x0, 0x0, 0x0, 0x0)
/Users/mk/work/juno/src/github.com/mkabischev/lodge/server/commands.go:38 +0x13e
github.com/mkabischev/lodge/server.(*setCommand).process(0x2b8140, 0xc820016b70, 0x3743e0, 0xc820016570, 0x0, 0x0, 0x0, 0x0, 0x0)
<autogenerated>:12 +0xce
github.com/mkabischev/lodge/server.(*Server).handleRequest(0xc8200165a0, 0xc820012460)
/Users/mk/work/juno/src/github.com/mkabischev/lodge/server/server.go:111 +0x439
created by github.com/mkabischev/lodge/server.(*Server).Serve
/Users/mk/work/juno/src/github.com/mkabischev/lodge/server/server.go:54 +0x133

echo "SET foo 100 -1\r\nhello\r\n 0" | nc localhost 20000