v0.7.1
Add :shelly to *features* only while 'shelly:interpret'ing.
Change the default version the install script installs to the latest version.

Because the stable version requires Perl5 and I suppose new users may
not expect it.
Invoke asdf:initialize-source-registry if a system-not-found error is handled.
Add the shlyfile directory to asdf:*central-registry* only while local shlyfile is loading.
Fix the message of 'upgrade' command.
Add options --no-core, --no-local-shlyfile, --no-global-shlyfile and --no-shlyfile.
Fix an error in case of when command action is not specified.
Add shelly:*argv*.
Release v0.7.2.
Merge branch 'v0.7.x'

Conflicts:
	shelly.asd