MEN-2282: Add commits check to mender-convert repo

Create a minimal .travis.yml to trigger the check

Changelog: Title

Signed-off-by: Lluis Campos <lluis.campos@northern.tech>

.gitignore

@@ -1,3 +1,4 @@
 input/
 output/
 device-image-shell/output
+mendertesting/

.travis.yml

@@ -0,0 +1,10 @@
+language: minimal
+
+dist: trusty
+
+before_script:
+    - git clone git://github.com/mendersoftware/mendertesting
+
+script:
+    # Check commit compliance.
+    - mendertesting/check_commits.sh