t: rename to _t to fix module support

The following two files contain characters which aren't valid in source
files within a Go module:

	t/.password-store/GoJira/api-token:gojira@corybennett.org.gpg
	t/.password-store/GoJira/api-token:mothra@corybennett.org.gpg

The directory only contains test scripts, so it doesn't need to be
included in the module. The simplest way to do that is to start the
directory with an underscore.

Fixes #228.

Makefile

@@ -84,8 +84,8 @@ clean:
 	rm -rf ./$(NAME)
 
 prove:
-	chmod -R g-rwx,o-rwx $(CWD)/t/.gnupg
-	OSHT_VERBOSE=1 prove -v 
+	chmod -R g-rwx,o-rwx $(CWD)/_t/.gnupg
+	OSHT_VERBOSE=1 prove -v _t/*.t
 
 generate:
 	cd schemas && ./fetch-schemas.py