Fix compiling for Liquid 4

Author: pushrax

liquid-c.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_dependency 'liquid', '~> 3.0.0'
+  spec.add_dependency 'liquid', '>= 3.0.0'
 
   spec.add_development_dependency "bundler", "~> 1.5"
   spec.add_development_dependency "rake"