MSRV

[daxpedda]

We recently increased the MSRV from 1.34 to 1.57. It shouldn't be too hard to lower the MSRV again, but seeing that we don't actually know who needs it at such a low MSRV we decided to actually wait for feedback.
Reducing the MSRV will slightly increase the maintenance burden for us, a cost that personally I'm willing to bear, but not needlessly.

So if you are a consumer of this library with a need for a lower MSRV, please drop by and leave a comment!