[travis] Add minimal .travis.yml file

Allow for automated builds via Travis CI (https://travis-ci.org).

Explicitly build just the wimboot.%.unsigned targets, since neither
the pesign nor gcab packages are in the allowed packages list for the
Travis 14.04 ("trusty") container environment.

Signed-off-by: Michael Brown <mbrown@fensystems.co.uk>

.travis.yml

@@ -0,0 +1,23 @@
+dist: trusty
+
+sudo: false
+
+language: c
+
+cache: ccache
+
+compiler:
+  - gcc
+
+addons:
+  apt:
+    packages:
+      - binutils-dev
+      - libiberty-dev
+
+env:
+  global:
+    - MAKEFLAGS="-j 4"
+
+script:
+  - make -C src wimboot.i386.unsigned wimboot.x86_64.unsigned