Integrate Etcher CLI in the main repository (#352)

This PR integrates the Etcher CLI code-wise, but doesn't yet handles the
distribution part of the story.

Signed-off-by: Juan Cruz Viotti <jviottidc@gmail.com>

lib/cli/utils.js

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2016 Resin.io
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict';
+
+const _ = require('lodash');
+const errors = require('resin-cli-errors');
+const chalk = require('chalk');
+
+/**
+ * @summary Print an error to stderr
+ * @function
+ * @public
+ *
+ * @param {(Error|String)} error - error
+ *
+ * @example
+ * utils.printError(new Error('Oops!'));
+ */
+exports.printError = function(error) {
+  if (_.isString(error)) {
+    error = new Error(error);
+  }
+
+  console.error(chalk.red(errors.interpret(error)));
+};