Merge branch 'release/0.8.0-RC.6' into develop
Updated version for next release cycle
Rename nodes-with-role to targets-with-role

targets-with-role returns a sequence of target maps and nodes-with-role
returns a sequence of nodes.
Add targets-in-group

Returns a sequence of target-maps for all targets with the specified
group name.
Fix os detection for CentOS
Fix aptitude commands for long package names

Use "disable-columns" option when running aptitude search to find
packages with long names.

Use aptitude --disable-columns when verifying packages are installed.
Only mirror permissions to state-root if needed

When mirroring permissions, only adjust the permissions if they do not
already match.  This is to prevent chmod, chown and chgrp errors.
Refactor state-root script into functions
Add :no-deref option to symbolic-link
Fix action :sudo-user with a :no-sudo admin user

When using :no-sudo in the admin user, ensure that an explicit
:sudo-user action option is honoured.

Fixes #300
Add argument checking for remote-directory
Improve propogation of cause in throw-phase-errors
Improve error handling in defmulti-plan
Allows for using crate-install by passing settings

Factors out install-from multi-method from the previous install
multi-method, which is preserved for compatibility.
Don't slurp files to calculate md5

Avoids out of memory errors on transferring large files from localhost.

Fixes #309
Updated project.clj, release notes and readme for 0.8.0-RC.7
Merge branch 'release/0.8.0-RC.7'