Clarify supported Git versions
Merge branch 'master' into development

* master:
  Specify MIT license in gemspec (GH-19)
Add gem version badge to readme
Add Travis CI badge to readme
Set `Twig::SUBCOMMANDS` to list of known subcmds
init-completion: Add completion for known subcmds
Readme: s/twigrc/twigconfig/
init-completion: Use `Twig::VERSION`
init-completion: Use `Twig::HOMEPAGE`
Update gemspec description
twig-rebase: Change STDIN to
Add subcommand completion to history
Add `Twig::Subcommands.all_names`
Add `Twig::Subcommands::BIN_PREFIX`
init-completion: Use `Twig::Subcommands.all_names`
Remove `Twig::SUBCOMMANDS`
Use `BIN_PREFIX` when detecting subcommands
Add completion for custom subcommands to history
Paginate help content where possible
Add basic `Cli#run_pager` specs