Add the php-imap module for catchers addon

Part of #24

Dockerfile

@@ -3,7 +3,7 @@ MAINTAINER Girish Ramakrishnan <girish@cloudron.io>
 
 # this can be removed in next base image update
 RUN apt-get update && \
-    apt-get install -y php7.0-zip crudini php7.0-soap && \
+    apt-get install -y php-zip crudini php-soap php-imap && \
     rm -rf /var/cache/apt /var/lib/apt/lists
 
 RUN mkdir -p /app/code