Misleading documentation on configuration's default values

[joaodelgado]

Some of the the default values from the README and the ones present in config module don't seem to match:

https://github.com/rust-lang-nursery/rls/blob/fb4dde72b198c8a17b2d72fbc9652daea6672c1c/src/config.rs#L139-L159

The configurations that seem to have a differente values are:

Config	Documentation	Implementation
cfg_test	true	false
workspace_mode	false	true

[joaodelgado]

I can work on this issue and update the documentation.

But I would also like to question the default configuration.

• cfg_test seems very useful when writing tests.
• As for workspace_mode, the readme states that it is still experimental and requires unstable_features, so it feels a bit weird to be enabled by default.

[nrc]

The code is right in both cases - setting cfg_test to true gives a whole bunch of erroneous dead code warnings, so should be off. workspace_mode is no longer unstable and is now on by default - the documentation about it being experimental is out of date.