support mv and pv override
add _autoPV option to determine whether to send automatical pv requests
fix syntax errors
add _autoPageTiming option
update README.md
update README.md
add _setReferrer and _setHref method
remove description about old apis
update README.md
update README.md
remove old hippo
migrate old hippo to cortex
remove argument `override`; support request id; deprecate hippo_perf_version
fix syntax error
update README.md
improve stability
user no underscore
improve the stability about the logic of request id
update version to override wrong file
add a new method "_setCustomConst", and deprecate "_setRequestId", "_setGuid"