use runtime.Caller to decipher template dir
use runtime.Caller to decipher template dir

msgp fails when GOPATH has multiple entries

A better way to grab the base path of the tmpl files is to start from the path of the current go file. runtime.Caller exposes this.

Fixes #36

fix missing import

appneta/msgp,dockbiz/msgp,darvik80/msgp,tinylib/msgp,kgrz/msgp,eliothedeman/msgp,appneta/msgp,jfbus/msgp,ebfe/msgp,DrGo/msgp,mengzhuo/msgp,skatsuta/msgp,tinylib/msgp,segmentio/msgp