add support for recordio and sparse matrices

[jesterhazy]

sklearn container should include support for reading and writing recordio and sparse matrices.

see aws/sagemaker-python-sdk#767 for more details.

[vanetoj]

mine is giving me "AlgorithmError: Exit Code: 127 "- and above " /usr/bin/env: 'python\r': No such file or directory" it happens during uploading of the generated model . does that mean it trained but something went wrong with uploading the results and what? i simply used your files but switched from decision tree to svm- regression. thank you!

[ChoiByungWook]

Another user is running into issues due to support for recordio not being present. aws/sagemaker-python-sdk#1093

[remanuelg]

2022 and still no support?
Could someone confirm if the support for BytesIO would be implemented through the sagemaker-training-toolkit?