Rename ':first_boot_attributes' option

When using knife-solo with knife-ec2 the --json-attributes option
would be assigned to ':json_attributes' rather than
':first_boot_attributes'.  This would prevent json attributes being
passed to knife-solo when running 'knife ec2 server create --solo'

Renamed the option here to match the option from knife-ec2.
Handle gem dependencies the ruby gems way
Changelog updates
Pre-release version bump
Match chef's latest version strings
Rebundle for latest gems
Ignore travis from manifest

Decided to also set up a proper ignore array.
Put dev gems back in for travis
Fix duplicate constant definitions for Ruby 1.8

Ruby 1.8.7 does not like the `||=` construction for Class constants,
so use `defined?` to check if the constants are already declared.

Fixes #169.
Fallback to :first_boot_attributes if :json_attributes not specified

`knife bootstrap` uses :first_boot_attributes and knife-ec2 copies the
value there. So if knife solo is injected directly to Knife::Bootstrap
and Bootstrap class initialized by e.g. knife-ec2 we need to support
that option, too.
Merge branch 'russellcardullo/json-options'

Closes PR #166.
Merge pull request #170 from tmatilai/ruby-1.8-constants

Fix duplicate constant definitions for Ruby 1.8
Bump version to 0.2.0.pre1 for development
Readme: Use `knife solo` to list the available commands
Fix copy&paste error in PR #169

Sigh.