chore: also install -g gulp on Travis (angular#2934)

This wasn’t necessary before, but it seems to be necessary now.

Author: chalin

scripts/before-install.sh

@@ -5,6 +5,4 @@ set -e -o pipefail
 [[ -z "$NGIO_ENV_DEFS" ]] && . ./scripts/env-set.sh
 [[ -n "$TRAVIS" ]] && . ./scripts/env-info-and-check.sh
 
-if [ -z "$TRAVIS" ]; then
-  (set -x; npm install -g gulp --no-optional)
-fi
+(set -x; npm install -g gulp --no-optional)