Added the binary_to_hex() function

We're going to need to convert binary buffers into hexadecimal strings in more
places as we add support for different backends.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Added missing include of <stdint.h> to sha1.h

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Added basic Amazon Glacier client

Currently, the only supported action is to list available vaults in a given
region.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>