Amp trainer

[alphinside]

Type of changes

Please check the type of change your PR introduces: - [ ] Bugfix - [x] Feature - [ ] Code style update (formatting, renaming) - [ ] Refactoring (no functional changes, no api changes) - [ ] Build related changes - [x] Documentation content changes - [ ] Other (please describe): ## What is the current behavior? We don't have any mixed precision training - close #62 Related issues : - depends on #17 , Need to address issue for pytorch version higher than 1.4.0 ## What is the new behavior?

• Add new trainer : AMPTrainer

Checklist

• [ ] Unit tests pass locally with my changes
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation (if appropriate)
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have filled the [Unreleased] Changelog

[triwahyuu]

we'll close this PR because it is no longer served purpose in pytorch lightning trainer backend @alphinside