Add sha-2 (commit 61155d)

Unfortunatley the sha2 project does not have versioned releases so we
use the latest commit.

We have also manually added a frontend to sha-2 to allow us to invoke
it from the command line, thanks bittrof for the help!

LICENSES/Unlicense.txt

@@ -0,0 +1,22 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute
+this software, either in source code form or as a compiled binary, for any
+purpose, commercial or non-commercial, and by any means.
+
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and
+to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of relinquishment
+in perpetuity of all present and future rights to this software under copyright
+law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH
+THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <http://unlicense.org/>