Update docker build script and tools

docker/Dockerfile

@@ -0,0 +1,20 @@
+FROM php:7.2-cli
+
+# Project folder
+RUN mkdir -p /srv/app
+
+WORKDIR /srv/app
+
+RUN apt-get update \
+    && apt-get install -y git zip curl gnupg \
+    && rm -rf /var/lib/apt/lists/*
+
+# get composer and required tools
+RUN curl -sLO https://getcomposer.org/download/1.6.3/composer.phar \
+    && mv composer.phar /usr/local/bin/composer \
+    && chmod +x /usr/local/bin/composer
+
+# Deployer
+RUN curl -sLO https://deployer.org/releases/v6.0.3/deployer.phar \
+    && mv deployer.phar /usr/local/bin/dep \
+    && chmod +x /usr/local/bin/dep