[added] ability to throw instead of warn

Author: ryanflorence

README.md

@@ -29,3 +29,9 @@ if (ENV === 'development') a11y();
 You probably don't want to call it if you're in production, and better
 yet, alias the module to nothing with webpack in production.
 
+If you want it to throw errors instead of just warnings:
+
+```
+a11y({throw: true});
+```
+

lib/__tests__/index-test.js

@@ -8,7 +8,7 @@ var k = () => {};
 var captureWarnings = (fn) => {
   var _warn = console.warn;
   var msgs = {};
-  console.warn = (msg) => msgs[msg.replace(/^Warning: /, '')] = true;
+  console.warn = (msg) => msgs[msg] = true;
   fn();
   console.warn = _warn;
   return msgs;

lib/index.js

@@ -1,30 +1,40 @@
 var React = require('react');
-var warning = require('react/lib/warning');
 var assertions = require('./assertions');
 
-var assertAccessibility = (tagName, props, children) => {
+var assertAccessibility = (tagName, props, children, log) => {
   var key;
 
   var tagTests = assertions.tags[tagName];
   if (tagTests)
     for (key in tagTests)
-      warning(tagTests[key].test(tagName, props, children), tagTests[key].msg);
+      log(tagTests[key].test(tagName, props, children), tagTests[key].msg);
 
   var propTests;
   for (var propName in props) {
     propTests = assertions.props[propName];
     if (propTests)
       for (key in propTests)
-        warning(propTests[key].test(tagName, props, children), propTests[key].msg);
+        log(propTests[key].test(tagName, props, children), propTests[key].msg);
   }
 };
 
-module.exports = () => {
+var error = (passed, msg) => {
+  if (!passed)
+    throw new Error(msg);
+};
+
+var warn = (passed, msg) => {
+  if (!passed)
+    console.warn(msg);
+};
+
+module.exports = (options) => {
   var _createElement = React.createElement;
+  var log = options && options.throw ? error : warn;
   React.createElement = function (type, _props, ...children) {
     if (typeof type === 'string') {
       var props = _props || {};
-      assertAccessibility(type, props, children);
+      assertAccessibility(type, props, children, log);
     }
     return _createElement.apply(this, arguments);
   };