Add JSHint and make dygraphs pass its checks. Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com> Author: Dan Vanderkam <dan@dygraphs.com>