bash-it search functionality: allow test to skip on travis

test/lib/helpers.bats

@@ -8,12 +8,14 @@ cite _about _param _example _group _author _version
 load ../../lib/helpers
 
 NO_COLOR=true
-IS_DARWIN=false
+
+IS_DARWIN=
 [[ "$(uname -s)" == "Darwin" ]] && IS_DARWIN=true
 
-if [ "$IS_DARWIN" == "true" ]; then
 @test "helpers search aliases" {
+  if [ -z "$IS_DARWIN" ]; then
+     skip 'search test only runs on OSX'
+  fi
   run _bash-it-search-component 'plugins' 'base'
   [[ "${lines[0]}" =~ 'plugins' && "${lines[0]}" =~ 'base' ]]
 }
-fi