Replaced default path when using --workspace

I haven't used exercism in a while and just updated to 3.0.11. In the process. I used the --workspace flag, but it ignored the path I gave and replaced the default (existing) path.

Steps taken:

1. `exercism configure --token=`
Result:
```
The default Exercism workspace is ~/Exercism
There is already something there.
...
You can choose the workspace location by rerunning this command
with the --workspace flag.
```
2. `exercism configure --token= --workspace=~/Exercism/Reboot/`
Result:
```
You have configured the Exercism command-line client:

Config dir: ~/.config/exercism
Token: (-t, --token)
Workspace: (-w, --workspace) ~/Exercism/Reboot
API Base URL: (-a, --api) https://api.exercism.io/v1
```

However, `~/Exercism/Reboot` does not exist. The existing directory `~/Exercism` is now an empty directory `~/exercism`.