Update deps and drop Clojure 1.5.1 and 1.6 support

[joelittlejohn]

• Updated encore and nippy (requires Clojure 1.7.0+)
• Updated AWS SDK to 1.12.x
• Other minor dep upgrades

[bitti]

Will this result in a release soon? The AWS SDK before version 1.12.261 is already flagged with an CVE: https://nvd.nist.gov/vuln/detail/CVE-2022-31159.

[roberttaylor426]

Hiya @kipz, just a gentle nudge on the above. Is a new release a possibility soon?

Thanks!

[joelittlejohn]

@roberttaylor426 let's do it!