Handle more edge cases (#3)

1. Disallow underscores
2. Allow single character usernames
3. Allow multiple hyphens, as long as they aren't next to each other

Author: dguo

README.md

@@ -21,11 +21,14 @@ regex().test('foo-bar'); // => true
 regex().test('foobar'); // => true
 regex().test('3foobar'); // => true
 regex().test('3foo-bar'); // => true
+regex().test('foo-bar-baz'); // => true
+regex().test('f'); // => true
 regex().test('foo-bar-'); // => false
 regex().test('-foo-bar'); // => false
 regex().test('foo--bar'); // => false
 regex().test('~derp@darp---++asdf'); // => false
 regex().test('[email protected]'); // => false
+regex().test('foo_bar'); // => false
 ```
 
 ## Why?

index.js

@@ -2,13 +2,13 @@
  * Expose username regex, following github conventions
  * like:
  * _Username may only contain alphanumeric characters
- * and only single hyphen, and cannot begin or end with hyphen._
+ * and only single hyphens, and cannot begin or end with a hyphen._
  *
  *
  * Example input:
  *   foo
  *   foo-bar
  */
 module.exports = function regexUsername () {
-  return /^\w+-?\w+(?!-)$/;
+  return /^([a-z\d]+-)*[a-z\d]+$/i;
 };

test.js

@@ -11,14 +11,22 @@ describe('username regex', function() {
   it('should match username input', function() {
     assert.equal(regex().test('foobar'), true);
     assert.equal(regex().test('foo-bar'), true);
+    assert.equal(regex().test('FooBar'), true);
+    assert.equal(regex().test('FOOBAR'), true);
+    assert.equal(regex().test('foo-bar-baz'), true);
+    assert.equal(regex().test('f'), true);
   });
 
   it('should catch incorrect input', function() {
     assert.equal(regex().test('-foo'), false);
     assert.equal(regex().test('foo-'), false);
+    assert.equal(regex().test('-'), false);
     assert.equal(regex().test('foo--bar'), false);
     assert.equal(regex().test('foo-bar-'), false);
     assert.equal(regex().test('3tobi--ferret'), false);
     assert.equal(regex().test('~~derp@darp-----++asdfasdf'), false);
+    assert.equal(regex().test('foo_bar'), false);
+    assert.equal(regex().test('_foobar'), false);
+    assert.equal(regex().test('foobar_'), false);
   });
 });