README.rdoc updated

== Changes

* README.rdoc - uninstallation process changed so no changes in application code provided.
Uninstallation removed

== Deletions

* rake uuids:uninstall task removed as potentially dangerous.
Setting custom UUID allowed [passes]

== Addons

* Uuids::Uuid.new can accept custom value of UUID.
* Uuids::Uuuid#value validation added.
* EN and RU translations added for UUID format validation error.

== Changes

* API documentation updated

This is necessary to allow populating uuids from some outer source.
Uuids::Base refactored [passes]

== Changes

* Uuids::Base.included made private.

== Refactoring

* Uuids::Base.define_scope (private).