Support day and week in duration parsing

[robherley]

Closes:

• Cannot specify signed URL TTL in days #65

tl;dr I just yoinked the time.ParseDuration from the stdlib and added some more units like 1w for one week (168 hours) and 1d for one day (24 hours)

now you can do something like:

echo "hello world" | ssh snips.sh -- -private -ttl 1w2d

cc @benwaffle

[benwaffle]

nice to know I can do -ttl 1w3ns