update readme for TF0.12

[holyjak]

what

• Describe high-level what changed as a result of these commits (i.e. in plain-english, what do these changes mean?)
• Use bullet points to be concise and to the point.

why

• Provide the justifications for the changes (e.g. business case).
• Describe why these changes were made (e.g. why do these commits fix the problem?)
• Use bullet points to be concise and to the point.

references

• Link to any supporting github issues or helpful documentation to add some context (e.g. stackoverflow).
• Use closes #123, if this PR closes a GitHub issue #123

[Gowiem]

/rebuild-readme

[Gowiem]

/test all

[Gowiem]

@holyjak Thanks for the contribution! Released as 0.8.1.