Update wp to 4.8

DESCRIPTION.md

@@ -1,4 +1,4 @@
-This app packages WordPress 4.7.5.
+This app packages WordPress <upstream>4.8</upstream>.
 
 WordPress is web software you can use to create a beautiful website or blog.
 We like to say that WordPress is both free and priceless at the same time.

Dockerfile

@@ -8,7 +8,7 @@ RUN apt-get update && \
 
 RUN mkdir -p /app/code
 WORKDIR /app/code
-RUN curl -L http://wordpress.org/wordpress-4.7.5.tar.gz | tar -xz --strip-components 1 -f -
+RUN curl -L http://wordpress.org/wordpress-4.8.tar.gz | tar -xz --strip-components 1 -f -
 RUN mv /app/code/wp-content /app/code/wp-content-vanilla && ln -s /app/data/wp-content /app/code/wp-content
 RUN ln -s /app/data/htaccess /app/code/.htaccess
 ADD wp-config.php.template /app/code/wp-config.php.template