brew: pass through TRAVIS_ variables.

bin/brew

@@ -66,9 +66,9 @@ then
 
   FILTERED_ENV=()
   # Filter all but the specific variables.
-  for VAR in HOME SHELL PATH TERM LOGNAME USER CI TRAVIS TRAVIS_SUDO SSH_AUTH_SOCK SUDO_ASKPASS \
+  for VAR in HOME SHELL PATH TERM LOGNAME USER CI TRAVIS SSH_AUTH_SOCK SUDO_ASKPASS \
              http_proxy https_proxy ftp_proxy no_proxy all_proxy HTTPS_PROXY FTP_PROXY ALL_PROXY \
-             "${!HOMEBREW_@}"
+             "${!HOMEBREW_@}" "${!TRAVIS_@}"
   do
     # Skip if variable value is empty.
     [[ -z "${!VAR}" ]] && continue