Add shell script sh/proofexist to submit hash only
Add shell script sh/proofexist to submit hash only

Will register hash, or else give its timestamp and blockstamp;
always outputs the approriate site link under detail.
Stand-alone script is fully commented.

Written pursuant to issue 20 raised by maraoz:
allow submitting documents by hash (no file needed)
https://github.com/maraoz/proofofexistence/issues/20

Passed test at https://git.io/victor
$ ./proofexist   # Will test using API demo hash.
In general, takes one argument, the hash itself
(which will be zero padded on the right if too
short, e.g. submitting a SHA-1 digest).

maraoz/proofofexistence,maraoz/proofofexistence,maraoz/proofofexistence,maraoz/proofofexistence