Rebased app secret proof
Fixed conflicts
Move app secret proof
More documentaion updates
Removed CSRF from signed request
Fix for order of validation on redirect helper
Merge pull request #287 from SammyK/refactor-app-secret-proof

[4.1] Refactored app secret proof handling
Merge pull request #293 from SammyK/more-doc-updates

[4.1] More documentaion updates
Merge pull request #294 from SammyK/remove-csrf-from-signed-request

[4.1] Removed CSRF from signed request
Merge pull request #297 from SammyK/check-for-code-first-redirect-helper

[4.1] Fix for order of validation on redirect helper