Update version and changelog for 0.4

[riyazdf]

Updated NOTARY_VERSION and the changelog - I did my best to sift through our milestone and issues/PRs to capture the changes. The link for the tag on our changelist won't resolve until the tag is published

[cyli]

Should we also add the bit about changing the import export format from zip to PEM?

[riyazdf]

@cyli: definitely. Done 👍

[HuKeping]

Are we ready for 0.4 now? I see there's still some issue under 0.4 milestone hasn't been closed yet.

[riyazdf]

Hi @HuKeping - thanks for checking in! This PR isn't officially releasing 0.4, since we'd be merging into the release candidate branch release/0.4. Once v0.4.0 is ready, we'll release the tag to master.

As for the remaining 0.4 issues - #735 has a PR open and #731 is half-complete (--rootkey flag) and the other half in a PR in progress. We'd like to get both in to a v0.4.X but they may not be critical for an initial RC or v0.4.0.

[HuKeping]

Hi @riyazdf does it make sense also add the relative PR link at the end of each line?

[riyazdf]

@HuKeping - definitely would be more than happy to!

[cyli]

LGTM on green! Thank so for keeping this up to date!

[endophage]

LGTM