Also, add support for hmac-sha1.
At the suggestion of AGL hmac-md5, and hmac-md5-96
support was not included.
Fixesgolang/go#3095.
R=golang-dev, agl, huin
CC=golang-dev
https://golang.org/cl/5696065
Manual edits to README.
Moved from main Go repository, deleted Makefiles, ran gofix -r go1rename.
Tested with: go test code.google.com/p/go.crypto/...
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5564059