Fix Docker builds

Dockerfile

@@ -1,15 +1,16 @@
 FROM php:5.6-apache
 RUN apt-get update
-RUN apt-get install -y libicu-dev xz-utils git zlib1g-dev python npm nodejs-legacy
+RUN curl -sL https://deb.nodesource.com/setup_6.x | bash -
+RUN apt-get install -y libicu-dev xz-utils git zlib1g-dev python nodejs
 RUN docker-php-ext-install mbstring
 RUN docker-php-ext-install intl
 RUN docker-php-ext-install zip
 RUN npm install -g bower grunt-cli
 RUN a2enmod rewrite
+RUN curl -sS https://getcomposer.org/installer | php
 COPY php.ini /usr/local/etc/php/
 COPY . /var/www/html/
-RUN curl -sS https://getcomposer.org/installer | php
-RUN php composer.phar install
+RUN php composer.phar install --prefer-dist
 RUN npm install
 RUN bower --allow-root install
 RUN grunt

composer.json

@@ -35,11 +35,6 @@
       "package": {
         "name": "rg3/youtube-dl",
         "version": "2016.09.08",
-        "source": {
-          "url": "https://github.com/rg3/youtube-dl.git",
-          "type": "git",
-          "reference": "2016.09.08"
-        },
         "dist": {
           "type": "tar",
           "url": "https://github.com/rg3/youtube-dl/archive/2016.09.08.tar.gz"

composer.lock

@@ -4,8 +4,8 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "94a6fb4af98949ac2c1e0abb3a372d97",
-    "content-hash": "1cdb3e32a6a07dbe8c26b861c6cf512b",
+    "hash": "b012f269a785a013725ff7f6cbf59df3",
+    "content-hash": "6745f521db34e3a535092cab5eec8afc",
     "packages": [
         {
             "name": "aura/session",
@@ -1424,11 +1424,6 @@
         {
             "name": "rg3/youtube-dl",
             "version": "2016.09.08",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/rg3/youtube-dl.git",
-                "reference": "2016.09.08"
-            },
             "dist": {
                 "type": "tar",
                 "url": "https://github.com/rg3/youtube-dl/archive/2016.09.08.tar.gz",