* VisualDL User Guide-English Version

* Update UserGuide-final-syx0706.md

* test: add test case

* feat: add chart tooltip in histogram overlay

* feat: add tooltip in histogram chart

* Add pr curve.

* chore: update dependencies

* fix: compatibility of safari (#674)

* chore: code polishment

* fix: calculate step width in tooltip (#672)

* doc: update readme

* feat: histogram

* Fix warning for hdfs

* Update docs.

* fix: graph export style missing

* bump 2.0.0-beta.6

* build: use stable channel of rust toolchain

* feat: support model graph from backend

* feat: add filename in graph api

* feat: support api token key in visualdl service

* Add --model to parameters.

* Add histogram, add hdfs.