re-apply changes from #91 for a clean commit history
remove `#quiet_system` as it is dead code by now
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.
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.
Use debian_gem for bootstrapping Debian Wheezy

The Omnibus installer does not support Debian 7.0 Wheezy yet.
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
Drop support for Debian 5.0 "Lenny"

It reached EOL already one year ago.
Extract debianoid codename fetching to a method
Use gem installation method for all unknown Debian versions

This covers all unreleased versions.
Use ternary operator instead of one-lines if-else statements
Clean up bootstrap tests
Append --omnibus-version to --omnibus-options

Also add unit test to verify that the specified options will
be passed to the Omnibus installer.
Fix copy&paste error in PR #169

Sigh.
Rename Cook command's `--skip-chef-check` option to `--no-chef-check`

Knife convention is to use "--no-option" or "--[no-]option". In that
case the "Mixlib::CLI" class allows the option with or without the "no".
And this gives also the opportunity to set the default on knife
configuration and then override it on command line.

The old "skip" option is left with a deprecation warning for some period
of time to maintain backwards compatibility.
Remove singleton instance variable for #operating_system

The method is only called once.
Get Chef version from `chef-solo --version`

Verify the version ourself with Get::Requirement.