Added --rm to docker run exemple

Because we don't want to keep a "temporary" docker container that is just used to run crx
Add a temp volume for user extension

and set it as workdir
Update README to use the workdir
Add doc to create crx alias
Woopsi missing $@ to append remaining parameters
Fixed crx alias
Fixed case where no path is given but should be required
Create crx-alias.sh
Update README.md
Merge pull request #1 from chadrien/user-friendly

User friendly