Fix Travis CI tests due to missing Snippy from master

The snippy folder was left after installing the snippy tool.
This caused likely problems while running the tests for the
plugin that had the 'snippy' cloned into the same directory
where the 'snippy-tldr' root path was.

Signed-off-by: Heikki Laaksonen <laaksonen.heikki.j@gmail.com>

.travis.yml

@@ -20,6 +20,7 @@ install:
 before_script:
   - git clone https://github.com/heilaaks/snippy.git
   - make -C snippy install QUIET=
+  - rm -rf snippy
 
 script:
   - make tests