Fix PRELEASE

MSP-9816
Fix branch in Travis-CI badgge

MSP-9816
Add rails-erd

MSP-9816
Metasploit::ERD.namespace_entities

MSP-9816

`Metasploit::ERD.namespace_entities` will find all
`ActiveRecord::Base.descendants` under a given namespace name.
Metasploit::ERD::Entity::Namespace

MSP-9816

Move Metasploit::ERD.namespace_entities to
Metasploit::ERD::Entity::Namespace#classes.
Ignore rake files for coverage

MSP-9816
Add missing YARD docs

MSP-9816
Metasploit::ERD::Entity::Class

MSP-9816

Metasploit::ERD::Entity::Class find all directly related classes through
belongs_to associations on the class.  In addition to
Metasploit::ERD::Entity::Class, this includes
Metasploit::ERD::Entity::Relationship, which handles finding the related
classes for each belongs_to association and the differences between
polymorphic and non-polymorphic associations.
Metasploit::ERD::Cluster

MSP-9816

Metasploit::ERD::Cluster iterately traces the belongs_to and
superclasses of a collection of root Classes to find all Classes that
are required in a cluster to match foreign keys with primary keys.
Class and Namespace clusters

MSP-9816
domain for classes and namespaces

MSP-9816

Metasploit::ERD::Domain is a mixin, which adds the #domain method that
converts the classes' cluster.class_set to a RailsERD::Domain.
Metasploit::ERD::Diagram

MSP-9816

Specialize RailsERD::Diagram::Graphviz with default options that work
well with Metasploit::ERD::Domain#domain.
Add missing spec for Metasploit::ERD::Diagram::DEFAULT_OPTIONS[:inheritance]

MSP-9816
Add default filetype of png

MSP-9816
Metasploit::ERD::Clusterable

MSP-9816

Rename Metasploit::ERD::Domain to Metasploit::ERD::Clusterable and add
 #diagram alongside #domain.  #diagram allows uses to simply do
entity.diagram.create to create a png ERD in the current directory.
Specs for diagram :basename and :directory

MSP-9816
Fix YARD docs

MSP-9816

Work around bug in YARD 0.8.7.3 where `attr_reader <name>` after an `@!attribute [r] <name>`
causes the `@!attribute` docs to be suppressed.  Fix see inclusion by
using correct (see) form instead of @see (see also) for documenting
diagram methods.
Fix diagram creation

MSP-9816

Diagram creation did not work because create is implemented in RailsERD
by using class-level callbacks and those callbacks are not inheritted,
so I copied RailsERD::Diagram::Graphviz's callbacks into
Metasploit::ERD::Diagram; added specs for callbacks and create; and
ensured that the save callback creates the parent directory so the
default save from RailsERD::Diagram::Graphviz won't raise an exception.
Install graphviz on travis-ci

MSP-9816
Merge branch 'feature/port'

Conflicts:
	lib/metasploit/erd/version.rb