Added newline to hash and json writers

The other writers all already add a newline, except for the
text writer. Since it might be significant, I decided against adding a newline there.

This behaviour change is backwards compatible in the sense that the approvals don't change. Once they change, they also add the newline.
Make it possible to override the defaults
Added configuration option for default format
Merge pull request #33 from markijbema/add-newline

Added newline to hash and json writers
Bump version
Add default rake task
Add license to gemspec
Lock dependencies to current major releases
Merge pull request #34 from markijbema/allow-to-configure-format

Allow to configure format
Bump version
Document basic CLI usage
Move CLI code to better location.

The user interface belongs outside of the `lib/approvals` directory.
I've more or less standardised on putting it in lib/cli.
Clarify CLI usage
Ditch utilities directory

NOTE: I broke the build and squashed commits.
You may need to fetch a completely fresh master. Sorry :/