add version script to update ethpm.json (#906)

scripts/version.js

@@ -0,0 +1,16 @@
+#!/usr/bin/env node
+
+// Synchronizes ethpm.json version number with package.json.
+// Useful to run as an npm script alogn with `npm version`.
+
+const fs = require('fs');
+const cp = require('child_process');
+
+const pkg = require('../package.json');
+const ethpm = require('../ethpm.json');
+
+ethpm.version = pkg.version;
+
+fs.writeFileSync('ethpm.json', JSON.stringify(ethpm, null, 2) + '\n');
+
+cp.execSync('git add ethpm.json');