1. refine quick start and pipeline doc
2. remove tf pytorch easynlp from requirements
3. lazy import for torch and tensorflow
4. test successfully on linux and mac intel cpu
5. update api doc

Link: https://code.alibaba-inc.com/Ali-MaaS/MaaS-lib/codereview/8882373

* add trainer interface
 * add trainer script
 * add model init support for pipelineadd pipeline tutorial and fix bugs 
 * add text classification evaluation to maas lib 
 * add quickstart and prepare env doc
 * relax requirements for torch and sentencepiece
 * merge release/0.1 and fix conflict
 * modelhub support for model and pipeline

 Link: https://code.alibaba-inc.com/Ali-MaaS/MaaS-lib/codereview/8868339