Check if we have enough disk space for docker

Part of #642

src/docker.js

@@ -8,6 +8,7 @@ exports = module.exports = {
 
     ping: ping,
 
+    info: info,
     downloadImage: downloadImage,
     createContainer: createContainer,
     startContainer: startContainer,
@@ -621,3 +622,15 @@ function removeVolume(app, name, callback) {
         callback();
     });
 }
+
+function info(callback) {
+    assert.strictEqual(typeof callback, 'function');
+
+    let docker = exports.connection;
+
+    docker.info(function (error, result) {
+        if (error) return callback(new DockerError(DockerError.EXTERNAL_ERROR, 'Error connecting to docker. statusCode: ' + error.statusCode));
+
+        callback(null, result);
+    });
+}