Allow multiple distribution-id

This allows multiple values in `distribution-id`; add by repeating the flag with new values e.g.:

```bash
s3deploy -bucket=mybucket -distribution-id=abcd -distribution-id=efgh
```

Fixes bep#142

Add 'ignore' flag

Via 'ignore' flag, you can exclude local files and keep remote objects stale that are matched with regexp.

Usage example:
```
s3deploy \
    -source=public/ \
    -bucket=example.com \
    -region=eu-west-1 \
    -key=$AWS_ACCESS_KEY_ID \
    -secret=$AWS_SECRET_ACCESS_KEY \
    -ignore="^unsynced-dir/.*$" \
    -v
```

Number of ignored items is not added to any stats count.

circleci: Bump Goreleaser

Fixes bep/homebrew-tap#1

Upgrade to Go 1.17

Updates bep/homebrew-tap#1

goreleaser: Update config to new version

release: Remove the 386 build

For now.

circleci: Update to Go 1.14.3

go mod tidy

Add Prefix param to ListObjectsPages

Unexport pathEscapeRFC1738