Switch from console.log to Utils.Methods.warn
Clean jsdoc
Fix previous commit, which adds warn instead of `console.log`.
Now warn uses console.warn if it is available, console.log if it is not,
and does nothing otherwise.

Note that perfDiagnostics.ts was removed in the previous commit.
Merge pull request #724 from palantir/warn

Switch from console.log to Utils.Methods.warn
Release version 0.20.5
Merge branch 'master' into multi-time-axis