Merge tag '0.5.3' into develop

clj-ssh-0.5.3
Updated version for next release cycle
Update doc profiles
Add links re ssh and background processes
Ensure literal key strings are handled correctly
Ensure literal keys get a non-blank comment

When adding a literal key, use "Added by clj-ssh" as the comment.
Updated version, release notes and readme for 0.5.4
Merge branch 'release/0.5.4'