Merge branch 'release0.2.6'
Merge branch 'release0.2.7'
Merge branch 'release0.2.8'
Merge branch 'master' of github.com:trema/trema
Merge branch 'release0.3.0'
Merge branch 'release0.3.1'
Merge branch 'release0.3.2'
Merge branch 'release0.3.3'
Merge branch 'release0.3.4'
Merge branch 'release0.3.5'
Merge branch 'release0.3.6'
Add 'trema port_down' command. See features/trema_commands/port_down.feature for its usage and details (refs #253)
Version bump to 0.3.7
Merge branch 'release0.3.7' into develop
Merge branch 'release0.3.7'
Make gem install work under non-default ruby path

Fixes #254

Before this commit build.rb expects 'ruby' as the interpreter path.
It leads to gem installation failure in environments where ruby 1.8
is provided as a different path such as 'ruby1.8'.
Version bump to 0.3.8
Merge branch 'release0.3.8'
vagrantfile and cookbooks added