Update PHP version

This also makes sure that we install the PHP7 version of APCu by explicitly specifying value.

Author: bakura10

Dockerfile

@@ -1,4 +1,4 @@
-FROM php:7.0.5-fpm
+FROM php:7.0.6-fpm
 
 COPY config/custom.ini /usr/local/etc/php/conf.d/
 
@@ -9,5 +9,5 @@ RUN apt-get update && apt-get install -y zlib1g-dev libicu-dev libpq-dev \
     && docker-php-ext-install pdo_mysql \
     && docker-php-ext-install pdo_pgsql \
     ## APCu
-    && pecl install apcu \
+    && pecl install apcu-5.1.3 \
     && docker-php-ext-enable apcu