Minor editing support change for Emacs.
Added firm version dependencies for the gems to prevent regression.
Minor fix to prevent the Ruby 1.8.7 warning on already initialized constant.

This is to prevent the Tree::VERSION being evaluated twice in gemspec under Ruby 1.8.7.
Ignoring some more Emacs specific files.
Updated use of JSON version 1.7.6.

Note that 1.7.7 breaks conversion from JSON (the `json_create`
call-back method does not work.)
Ignoring the Ack search settings.
Added a ctags ignore.
Added debugger support for development.

Also added debugger to the :test bundler group.