Update() now updates the placeholder text. Issue #100

Update() updates the placeholder text, this way you can call update after changing the placeholder text and it will update (https://github.com/jDramaix/gwtchosen/issues/100).
Ability to style individual items in the ChosenListBox and indent them

Ability to style individual items in the Chosen list and indent them, we have used this to show hierarchy within the ChosenListBox, and you can also add a style name to items. For example you might want the user to select from a file structure so you want the directories to be at a different level then their children, but all of the items (files and directories) are valid options for the user to select.
Fixed indentation and Javadoc comments per Julien Dramaix's suggestions.
https://github.com/jDramaix/gwtchosen/pull/101
Added a convenience addStyledItem method.

Per Julien Dramaix's suggestion, added a convenience method,
public void addStyledItem(String label, String value, String className).
(see https://github.com/jDramaix/gwtchosen/pull/101 for details)
Filled in the missing pieces of addStyledItem(..) method's
functionality:

- Num. of pixels per indent level now comes from chozen.css
- Indented items "flatten" when appearing as search results
- The Sample app demonstrates the use of addStyledItem(..)
Merged branch 'master' of github.com:jDramaix/gwtchosen

- Conflict resolved: plugin/src/main/java/com/watopi/chosen/client/ChosenImpl.java
- Rearranged new methods in ChosenOptions to fit code style
- Made a minor improvement to the Sample
Added methods for adding/inserting styled/indented items to groups.

- Added five new methods for adding/inserting styled/indented items to groups
- Updated the Sample to inform about the option of mixing groups and indented items
Two minor code style fixes.
Merge pull request #101 from shawkinson-apptio/master

Update() now updates the placeholder text. Issue #100 and Ability to style individual items in the Chosen list and indent them