add beta-vae torch version

[everdark00]

All Submissions Basics:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you checked all Issues to tie the PR to a specific one?

All Submissions Cores:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?
• Does your submission pass tests, including CircleCI, Travis CI, and AppVeyor?
• Does your submission have appropriate code coverage? The cutoff threshold is 95% by Coversall.

New Model Submissions:

• Have you created a .py in ~/pyod/models/?
• Have you created a _example.py in ~/examples/?
• Have you created a test_.py in ~/pyod/test/?
• Have you lint your code locally prior to submission?

[yzhao062]

thanks for the PR! could you resubmit it to the development branch?

[coveralls]

Pull Request Test Coverage Report for Build 9035805756

Details

• 0 of 148 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.4%) to 92.331%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyod/models/vae_torch.py	0	148	0.0%

Totals
Change from base Build 8309424051:	-1.4%
Covered Lines:	9005
Relevant Lines:	9753

---

💛 - Coveralls

[yzhao062]

please resubmit this PR the development branch. thank you!