Add failing test: Tagged caching (driver "redis")

This test passes with cache driver "array" but fails with cache driver "redis". I came across the issue in my own app and double-checked with a fresh vanilla 4.3 install. My Redis installation should be alright.

Could not find the problem myself but just realized that the test passes when line 114 is changed to ```Cache::tags('tag')->put('data', $data, 100);``` so the tags()->forever() combo appears to be the issue.

PS: Hope I got the new bug report flow right.