Enum.md

+Enum type manager. It creates a separated class to hold each enum set, that can be used by multiple models, and also keeps the database data consistent. The enum type is shown to have a better performance against string- and integer-like enums.
+
+# How it works
+
+### Migration
+
+First you have to create the enum during your migration, since the database that holds the list of possible values.
+```ruby
+create_enum :status, %i(created draft published archived)
+```
+
+Some other examples are:
+```ruby
+# ['status_foo', 'status_bar']
+create_enum :status, %i(foo bar), prefix: true
+# 'foo_tst', 'bar_tst']
+create_enum :status, %i(foo bar), suffix: 'tst'
+```
+
+Then you can also manage this type along other migrations, like rename, add values, or delete it.
+```ruby
+# Rename enum by renaming the type it represents
+rename_type :status, :content_status
+
+# Adding values
+add_enum_values :status, %i(baz qux)                      # To the end of the list
+add_enum_values :status, %i(baz qux), prepend: true       # At the beginning of the list
+add_enum_values :status, %i(baz qux), after: 'foo'        # After a certain value
+add_enum_values :status, %i(baz qux), before: 'foo'       # Before a certain value
+add_enum_values :status, %i(baz qux), prefix: true        # With type name as prefix
+add_enum_values :status, %i(baz qux), suffix: 'tst'       # With a specific suffix
+
+# Deleting an enum by dropping the type it represents
+drop_type :status
+```
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