Gemfile cleanup

I have moved guard-test to its own gem-group called 'tools', which is recommended. I've also tried to dissolve the group containing gems for both the test environment and the development environment. These environments are **not** the same and does not contain the same gems by default.

However, since I do not use guard for anything, I cannot confirm that it is working. I suspect that I may have put them in wrong group or done something else wrong. Anyone who utilizes these tools should confirm the changes.