Merge pull request #84 from habuma/master

SOCIAL-255: Added ProviderSignInInterceptor and calls to interceptors during ProviderSignInController's sign-in flow. Does not address cases where PSIC must redirect to application-defined signup process.
Merge pull request #85 from habuma/master

Added ProviderSignInInterceptor and calls to interceptors during ProviderSignInController's sign-in flow. Does not address cases where PSIC must redirect to application-defined signup process.
Merge pull request #86 from habuma/master

SOCIAL-349: Allow for non-standard parameters to be sent in OAuth authorization flow.
Merge pull request #87 from habuma/master

SOCIALTW-37: Fix for character encoding problems in multipart posts.
Merge pull request #88 from habuma/master

Polish on Spring Social/Security code.
Merge pull request #89 from habuma/master

Polish