Refactor of module to allow extension via configuration

Added some new val in RoutesHelper to provide the paths to some css/javascript files (like JQuery or Bootstrap)
used by SecureSocial. By default the use the files provided by SecureSocial.

This lets users to replace these files without having to create a new Template object

A new custom CSS file has been added (default: empty path) to allow injection of custom styles to SecureSocial pages

Notes: this could be probably extended to all other custom images/icons of SecureSocial to facilitate integration with user apps
Updated documentation

Updated documentation with the changes to RoutesHelper
- Changed the save() method in UserService to return an Identity so that event callback implementations can receive Identity instances from custom classes.
Merge branch 'master' of github.com:jaliss/securesocial
Merge pull request #141 from platypii/master

Option to auto-login after completing signup.
Merge pull request #138 from pvillega/master

Static files injection to SecureSocial
updated change log
Adding XING and Foursquare Providers

Conflicts:
	samples/scala/demo/conf/play.plugins
added Foursquare and XING Providers
Merge pull request #143 from poornerd/master

XING and Foursquare pull request
added credits for the Xing and Foursquare providers
VK provider was added.
remove bad venue ID from Foursquare(™) Provider
Merge pull request #148 from poornerd/master

Remove incorrect parameter from Foursquare (tm) user/self API call
Add new Instagram Provider
Merge branch 'master' of https://github.com/jaliss/securesocial
simplified chinese message

Add Simplified Chinese message file
clean up instagram provider

thanks Jorge...
Merge pull request #151 from wuhaixing/master

Simplified Chinese message
Merge pull request #145 from KonstantinGrigoriev/master

VK.com provider