Various fixes to unbreak the codebase & testing

[dmikushin]

Dear Authors, thank you for bringing facebookresearch / loop to the world!

This PR aggregates small fixes to various problems seen during pretrained models testing:

• SPTK path actually needs one extra "/bin/" node
• Implicit conversion from float to integer is disliked by Python in multiple places
• Adding appropriate imports of Phenomizer components
• Changing test example to generate voice for some random text, which should be more interesting for a curious user

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at cla@fb.com. Thanks!

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!