Update knife-linode README

Update the README for the knife-linode gem to fix example and link to
Chef Docs.

[knife-206]
Merge pull request #23 from opscode/adamed-knife-206

KNIFE-206: Update knife-linode README
Add Linode configuration parameters to the (new) Ohai hints
Merge pull request #25 from opscode/adamed-knife-343

KNIFE-343: knife-linode: need access to assigned private IP address (etc)
Add first_boot_attributes support
Merge pull request #27 from opscode/adamed-knife-339

KNIFE-339: Add first_boot_attributes support
[KNIFE-362] Use a sane default for the Linode image parameter
Merge pull request #28 from opscode/adamed-knife-362

[KNIFE-362] Use a sane default for the Linode image parameter
config values should not take precedence over command line options
Merge pull request #30 from opscode/adamed-knife-383

KNIFE-383: config values should not take precedence over command line options
Merge remote-tracking branch 'opscode/master'