hardwired dependencies for execjs

The hard-wired requires cause commit hook to blow up on 'execjs not found' even if the JS tests are explicitly turned off.

	from /home/jakub/.rvm/gems/ree-1.8.7-2011.03/gems/execjs-1.2.6/lib/execjs.rb:5
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
	from /home/jakub/.rvm/gems/ree-1.8.7-2011.03/gems/pre-commit-0.1.16/lib/pre-commit/checks/js_check.rb:3
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
	from /home/jakub/.rvm/gems/ree-1.8.7-2011.03/gems/pre-commit-0.1.16/lib/pre-commit/checks/jslint_check.rb:1
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
	from /home/jakub/.rvm/gems/ree-1.8.7-2011.03/gems/pre-commit-0.1.16/lib/pre-commit/checks.rb:7
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
	from /home/jakub/.rvm/gems/ree-1.8.7-2011.03/gems/pre-commit-0.1.16/lib/pre-commit.rb:1
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:58:in `gem_original_require'
	from /home/jakub/.rvm/rubies/ree-1.8.7-2011.03/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:58:in `require'
	from .git/hooks/pre-commit:3