v0.8.0

This release includes pretty huge refactors. The config now uses Habitat, and there's a new AwsStorageConfig class for some better type-safety. Some of the config options are a little different:

- c.storage = :aws
+ c.storage = Sitemapper::AwsStorage

- c.aws_config = {"key" => "...", ...} 
+ c.aws_config = AwsStorageConfig.new(key: "...", ...)

The build block no longer works as a mini DSL. Instead, it passes the builder instance as an arg, but the add() methods are chainable.

- Sitemapper.build do
-   add("...")
-   add("...")
-   some_method(itself)
- end

+ Sitemapper.build do |builder|
+   builder.add("...").add("...")
+
+   some_method(builder)
+ end