#248 Error handling.

Added error handling functions for the change password view. This includes password confirmation error handling where the advisor inputs the same new password twice, and rendering the server side errors to the screen in their respective divs. Also added some on success handlers. Upon a successful submission the text fields clear, and a success message is rendered but for some reason I can't get the styling to work. Probably a simple mistake, but I wanted to get something in to make sure the approach at least looked okay. Still need to animate the dropdown, and also decide if we want to add the shake feature when an error is rendered like how we do with the registration form.
This function can be even simpler with an early return:
```js
if (!this.state.message) {
  return null;
}

// Just set `message` to 'Success!' in the success handler below.
return (
  <div id="message">
    <label className={this.state.success ? 'success' : 'error'}>
      {this.state.message}
    </label>
  </div>
);
```