cache kafka download

It takes 30s to pull from apache, which is a bit pointless

.gitignore

@@ -4,7 +4,7 @@
 .*
 
 # Downloads
-kafka.tgz
+/.downloads
 
 # Compiled Object files, Static and Dynamic libs (Shared Objects)
 *.o

.travis.yml

@@ -19,6 +19,10 @@ addons:
 services:
   - postgresql
 
+cache:
+  directories:
+    - .downloads
+
 install:
  - go get github.com/constabulary/gb/...
 

scripts/install-local-kafka.sh

@@ -4,15 +4,19 @@
 
 set -eu
 
+cd `dirname $0`/..
+
+mkdir -p .downloads
+
 # The mirror to download kafka from is picked from the list of mirrors at
 # https://www.apache.org/dyn/closer.cgi?path=/kafka/0.10.2.0/kafka_2.11-0.11.0.2.tgz
 # TODO: Check the signature since we are downloading over HTTP.
 MIRROR=http://apache.mirror.anlx.net/kafka/0.11.0.2/kafka_2.11-0.11.0.2.tgz
 
 # Only download the kafka if it isn't already downloaded.
-test -f kafka.tgz || wget $MIRROR -O kafka.tgz
+test -f .downloads/kafka.tgz || wget $MIRROR -O .downloads/kafka.tgz
 # Unpack the kafka over the top of any existing installation
-mkdir -p kafka && tar xzf kafka.tgz -C kafka --strip-components 1
+mkdir -p kafka && tar xzf .downloads/kafka.tgz -C kafka --strip-components 1
 # Start the zookeeper running in the background.
 # By default the zookeeper listens on localhost:2181
 kafka/bin/zookeeper-server-start.sh -daemon kafka/config/zookeeper.properties