Use 'make test-results' in travis-build script

.ci/proveit.sh

@@ -1,8 +0,0 @@
-#!/bin/sh
-set -e
-
-if ! prove -e cat -f "$1"
-then
-  cat "$1"
-  exit 1
-fi

.ci/travis-build.sh

@@ -16,5 +16,5 @@ make -j2 $EXTRA
 if [ "$TEST" != "NO" ]
 then
   make tapfiles
-  find . -name '*.tap' -print0 | xargs -0 -n1 ./.ci/proveit.sh
+  make -s test-results
 fi