Remove unnecessary installs

Author: Pedro Piñera

.travis.yml

@@ -8,8 +8,6 @@ matrix:
     - os: osx
       osx_image: xcode9.4
       xcode_scheme: ReactiveTask
-      before_script:
-        - gem install xcpretty
       script:
         - set -o pipefail && xcodebuild -workspace "$TRAVIS_XCODE_WORKSPACE" -scheme "$TRAVIS_XCODE_SCHEME" test | xcpretty
       env: JOB=Xcode9.4
@@ -24,8 +22,6 @@ matrix:
       env: JOB=SWIFTPM_DARWIN
     - os: osx
       osx_image: xcode9.4
-      before_script:
-        - gem install cocoapods
       script:
         - pod repo update
         - pod spec lint --quick