legal: include LICENSEs for data files

We depend upon data files from golang arch sub-repo and the Opcodes XML
database (behind PeachPy). This change includes their LICENSE files.

Updates #22

script/data

@@ -1,14 +0,0 @@
-#!/bin/bash -ex
-
-datadir="internal/data"
-
-dl() {
-    url=$1
-    name=$(basename ${url})
-
-    mkdir -p ${datadir}
-    curl --output ${datadir}/${name} ${url}
-}
-
-dl https://raw.githubusercontent.com/golang/arch/master/x86/x86.v0.2.csv
-dl https://raw.githubusercontent.com/Maratyszcza/Opcodes/master/opcodes/x86_64.xml