Change build script to build latest release versions if not in CI (#115)

Build.sh can build the latest versions of the images using the VERSION file under the two repos (core & web).

build.sh

@@ -4,13 +4,21 @@ set -e
 
 # Use this script to build docker images.
 
-if [ "$TRAVIS_BRANCH" = "master" ]; then
-    TAG="latest"
+if [[ "$TRAVIS" ]]
+then
+	if [ "$TRAVIS_BRANCH" = "master" ]; then
+		CORE_TAG="latest"
+		WEB_TAG="latest"
+	else
+		CORE_TAG="$TRAVIS_BRANCH"
+		WEB_TAG="$TRAVIS_BRANCH"
+	fi
 else
-    TAG="$TRAVIS_BRANCH"
+    CORE_TAG=`cat core/VERSION`
+    WEB_TAG=`cat web/VERSION`
 fi
 
 DOCKER=docker
 
-$DOCKER build -t maxking/mailman-core:$TAG core/
-$DOCKER build -t maxking/mailman-web:$TAG web/
+$DOCKER build -t maxking/mailman-core:$CORE_TAG core/
+$DOCKER build -t maxking/mailman-web:$WEB_TAG web/