Delete & Ignore output.txt & error.txt

Both output.txt and error.txt are produced by tests.
Each file contained a header that was overridden upon executing said
tests causing tracked files to be changed.

Added them to a local .gitignore file for this module.

Author: Lyndon Armitage

module/.gitignore

@@ -0,0 +1,2 @@
+error.txt
+output.txt