code: function walkDeclaration(decl, environment, replacements) {
      decl.value = decl.value.replace(functionRegex, function (match, value) {
          verifyParameters(replacements, value, decl, environment);
  
          return replacements[value][environment];
      });
  }
docs: Parses one CSS-declaration from the given AST and checks for
  possible replacements
  
  @param {Declaration} decl - one CSS-Declaration from the AST
  @param {String} environment - current environment
  @param {String} replacements - Object containing all replacements that we
  have inside the options