Fix spec helper on MacOS

If the detected path to Chrome includes spaces (which is does
by default on MacOS) then the version check command would fail,
preventing the test suite from running.

spec/spec_helper.rb

@@ -4,6 +4,7 @@
 $LOAD_PATH.unshift("#{CUPRITE_ROOT}/lib")
 
 require "fileutils"
+require "shellwords"
 require "bundler/setup"
 require "rspec"
 
@@ -15,7 +16,7 @@
 
 puts ""
 command = Ferrum::Browser::Command.build(Ferrum::Browser::Options.new, nil)
-puts `'#{command.path}' --version`
+puts `'#{Shellwords.escape(command.path)}' --version`
 puts ""
 
 Capybara.save_path = File.join(CUPRITE_ROOT, "spec", "tmp", "save_path")