fix(activate): prepare and pass env vars to serverless-api activateBuild

[philnash]

The activate command wasn't passing any environment variables to the new environment. This should fix that along with serverless-api#49.

Fixes: #109

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[philnash]

This is failing because of the updated types in serverless-api. It needs a release there, and a version bump here to work.

[dkundel]

I merged the other one but haven't released. Feel free to release a new version of serverless-api and then update this PR and merge :)