Merge pull request #2529 from maxwell-k/terraform_linter

Add a terraform linter

test/command_callback/test_terraform_terraform_command_callback.vader

@@ -0,0 +1,9 @@
+" Based upon :help ale-development
+Before:
+  call ale#assert#SetUpLinterTest('terraform', 'terraform')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The default command should be correct):
+  AssertLinter 'terraform', ale#Escape('terraform') . ' fmt -no-color --check=true -'