Add test for incorrect indentation, add Travis CI

.travis.yml

@@ -0,0 +1,8 @@
+language: c
+sudo: false
+
+notifications:
+  email: false
+
+script:
+  - ./tests.sh

tests.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+
+SPACED=$(grep -REn '^ .+' --include '*.snippets' snippets);
+
+if [[ -n SPACED ]]; then
+  echo These snippet lines are indented with spaces:;
+  echo;
+  echo "$SPACED";
+  echo;
+  echo Tests failed!
+  exit 1;
+fi
+
+echo Tests passed!
+exit 0;