Bump the version to 0.7.0

[RHL120]

Checklist

• [ ] Closing issues: #issue
• [X] Mark this if you consider it ready to merge
• [ ] I've added tests (optional)
• [ ] I wrote some documentation

Description This PR bumps the version to 0.7.0. This is necessary because of the windows fix: https://github.com/radareorg/r2pipe.rs/pull/51.

[RHL120]

@meme should I bump the edition to rust 2021?

[meme]

I don't think we should bump the edition yet until we have a use-case for 2021 features. I've released 0.7.0. Thanks.