Merge tag 'pallet-0.8.0-beta.8' into develop

pallet-0.8.0-beta.8
Updated version for next release cycle
Fix missing space in script prolog
Add pallet.api/version for the pallet version

Returns a map with :version and :revision keys.  When run from source, these
will return :unknown.
Add :no-checkouts profile

Used to disable lein checkouts when running tests prior to release.
Add clj-schema checks for specs, user, converge and lift
Fix hostname keyword in show-nodes
Fix os-version in show-nodes
Use assert for error message on unbound session
Correct error message for group without count
Add group-nodes test
Don't set :node-filter for group-name based groups

Do not set the :node-filter on a group for groups based on :group-name
membership, so that functions that modify the group-name don't have to worry
about updating the :node-filter function.
Remove environment option from cluster-spec
Fix node-spec when called without options
Enable phase specification of execution-settings-f
Ensure logged image-user passwords are obfuscated
Fix maybe-update-in for multi-argument case
Remove obsolete sessiion-with-environment
Name anonymous function for merged phase functions
Improve logging in spec-from-project