Fixed nasty SHA1 update bug.

The rounds for SHA1 included modifying the data as it’s transformed. This
caused problems when using the data stream more than once after the SHA1
update was completed. This is fixed by copying the block locally before
running the transform.
Updated semantic version to 0.2.1.
Merging fix for nasty SHA1 update bug.

* SHA1 transform modified data, altering it for any other algorithms
using it after SHA1 was done with it.
* Updated semantic version to 0.2.1 for Mac.
Merge pull request #4 from gibwar/develop

Fix for SHA1 update bug.