Megfile

- feat
- auto decode http content when response with `Content-Encoding` header
- perf
- add s3 retry code, retry request when catch response code `499`
- add environments for setup retry times: `MEGFILE_MAX_RETRY_TIMES`, `MEGFILE_S3_MAX_RETRY_TIMES`, `MEGFILE_HTTP_MAX_RETRY_TIMES`, `MEGFILE_HDFS_MAX_RETRY_TIMES`, `MEGFILE_SFTP_MAX_RETRY_TIMES`. default is `10`

- feat
- Support more official S3 configurations. New env: `AWS_ENDPOINT_URL_S3`, `AWS_ENDPOINT_URL`.

- perf
- optimize read and write performance for s3, http and hdfs

- fix
- fix `smart_glob` bug of s3 path with profile name

- feat
- support `-f` / `--follow` in `tail` command
- fix
- fix `smart_copy` bug in the function registered by `atexit`

- feat
- command `ll` show file count
- perf
- support new err for sftp to retry