add small test runner

allows tape users to do "tape test/*.js" so they can have something that
will run their tests under "npm test".

bin/tape

@@ -0,0 +1,8 @@
+#!/usr/bin/env node
+
+var path = require('path');
+process.argv.slice(2).forEach(function(file) {
+    require(path.resolve(process.cwd(), file));
+});
+
+// vim: ft=javascript

package.json

@@ -3,7 +3,7 @@
     "version" : "0.2.2",
     "description" : "tap-producing test harness for node and browsers",
     "main" : "index.js",
-    "bin" : {},
+    "bin" : "./bin/tape",
     "directories" : {
         "example" : "example",
         "test" : "test"