[ci] Specify a dummy install command so cpanminus is not invoked, sin…

…ce it doesn't know what to do with Parrot

.travis.yml

@@ -2,6 +2,7 @@ language: "perl"
 perl:
     - "5.10"
     - "5.14"
+install: "echo"
 before_script:
 # This stuff used to be required, but was rolled into the Travis CI perl support.
 #    - sudo apt-get install libffi-dev libicu-dev libgmp3-dev clang llvm-dev liblocal-lib-perl zlib1g-dev gcc-multilib