A warning displays when models are exporting models

[ryanhausen]

The following warning displays on export from the CLI:

UserWarning: Warning: monkeytype is not installed. 
Please install https://github.com/Instagram/MonkeyType to enable Profile-Directed Typing in TorchScript. 
Refer to https://github.com/Instagram/MonkeyType/blob/master/README.rst to install MonkeyType.

We may want to install it to avoid the warning. I am not sure if it affects performance.

[jamienoss]

After installing monkeytype the following error is produced when running: python flfm/cli.py export --n_steps=10 --out="testmodel"

Error: Unable to infer types. Please format the inputs to type `List[Tuple]` or `Dict[Callable, List[Tuple]]` to be run with MonkeyType.

[jamienoss]

Note that the env var FLFM_DEBUG_CLI can be used to get actual tracebacks from the CLI.