Added symbolic link "aerospike" to current directory.

This makes it possible to use:
import "github.com/aerospike/aerospike-client-go/aerospike", as required by some Go-IDE's (among which IntelliJ);

This way, we follow the Go-guidelines at: https://golang.org/doc/code.html#Workspaces
I quote: "src contains Go source files organized into packages (one package per directory)"