RuboCop cleanup

Whitespace, single quotes over double-quotes, etc.
Clean up attributes, metadata, README

* Name the cookbook in metadata
* Add `nginx` as a dependency to metadata
    * The `nginx_proxy` recipe needs it, so it’s a dependency
* Clean up attributes
* Rewrite README:
    * Represent attributes more cleanly
    * Set a better example for using the cookbook via wrapper cookbook
* Add `supports` to clearly specify targeted OS versions
Clean up nginx_proxy recipe

Consistency is key

* Align resource attributes’ arguments
* Use strings for modes
Drop unnecessary attributes for URL construction

Dynamically assigned attributes are best set inside recipes, but
better yet is to not use them when unnecessary.

The URL to download Archiva is only needed once, so there’s no need to
set it as an attribute.
Clean up default recipe

* Align resources’ attributes’ arguments
* Remove potentially inaccurate comment
    * Depending on attributes, it might not be installed in `/opt`
Properly use archiva home attribute for paths

Absolute paths means broken code if the attribute changes elsewhere.

This ensures we are consistent in the attribute usage.
Ensure node attributes are accessed consistently
Include apt::default to ensure `apt-get update` is run

Otherwise, convergences will fail on slightly out-of-date systems
E.g., Debian 7.2, Ubuntu 12.04
Add ignore files
Add CHANGELOG
Don't make Archiva jetty config file executable

No need for a config file to have exec enabled
Refactor nginx_proxy recipe to include default

Can't really have one without the other, and this
ensures that the `service[archiva]` resource is properly
available in the `nginx_proxy` recipe
Merge pull request #4 from evertrue/clean-up

Clean up cookbook, prep for larger refactoring