introduce travis/shellcheck

.travis.yml

@@ -0,0 +1,12 @@
+sudo: required
+dist: trusty
+
+before_install:
+  - echo 'deb http://archive.ubuntu.com/ubuntu trusty-backports main restricted universe multiverse' | sudo tee -a /etc/apt/sources.list
+  - sudo apt-get -qq update
+  - sudo apt-get install -y shellcheck
+
+git:
+  depth: 3
+
+script: ./shellcheck.sh

shellcheck.sh

@@ -0,0 +1,4 @@
+#!/bin/sh -ev
+# Shellcheck the script
+
+shellcheck install.sh