release binaries and docker images for arm64 (fullstorydev#170)

* goreleaser creates arm64 release binaries
* add multi-arch docker build; includes arm64

fix local storage quota errors (fullstorydev#141)

- don't store entire RPC response since it's not even used; only store
  the minimum response info for rendering item in history
- limit storage for a single key to 1mb -- most grpcui instances will
  have only one key, so this should keep us well under normal quota
  (which is 5mb)
- even after above limit, if we still hit quota issue: don't blow up!
  instead, log the error and keep going

since go 1.15 no longer supports darwin/386 builds, exclude that from…

… goreleaser

improve some sharp edges of request timeout validation (fullstorydev#76)

fix go.mod for go 1.13 (fullstorydev#47)

add Dockerfile (fullstorydev#43)

add goreleaser config (fullstorydev#16)