make_video(): add parameters for fps and output destination

[mkornacker]

1. fps parameter:

• make_video() currently produces videos at a fixed 25 fps.
• instead, it should accept an optional parameter (default: 25, or maybe 30) 'fps' which will be applied at runtime.

2. skip None frames
3. specify output destination:

• currently, .mp4 files are written into the current directory
• add kw parameter for the output destination (which could be a local directory or a prefix for an external URL such as an S3 bucket) and write it there