make hmacs updateable.
hmac reset after digist.
added tests for reset and update mechanism.
new sjcl.js
Revert "new sjcl.js"

This reverts commit 9187bdda633035f3e9369bfda01ce91af208b77e.
Merge pull request #102 from bitwiseshiftleft/feature/hmac_updatable

Feature/hmac updatable