Update analyzer and build dependencies

Merge pull request #167 from davidmorgan/release-1-1-1

Release 1.1.1

Allow quiver 0.25.

Merge pull request #163 from davidmorgan/allow-quiver-25

Allow quiver 0.25.

Customizable toString, improved generated output

• Version bump to 1.0.0. Three minor features are marked as experimental and
  may change without a major version increase: BuiltValueToStringHelper,
  JsonObject and SerializerPlugin.
• Made toString() output customizable.
• Made the default toString() output use indentation and omit nulls.
• Sort serializers in generated output.

Ignore nulls when deserializing with StandardJsonPlugin

• Ignore nulls when deserializing with StandardJsonPlugin.

Serialize DateTime, JsonObject, convenience methods, doubles.

• Add serializer for "DateTime" fields.
• Add JsonObject class and serializer.
• Add convenience methods Seralizers.serializeWith and deserializeWith.
• Add example for using StandardJsonPlugin.
• Support serializing NaN, INF and -INF for double and num.

Serializable "num", more flexible factory, bug fixes

• Add serializer for "num" fields.
• Better error message for missing serializer.
• Fix generation when there are nested multi-parameter generics.
• Use cascades in generated code as suggested by lint.
• Allow users to define any factory that references the generated implementation.
• Add example of a simpler factory for a one-field class.

Better checking, lintable generated code, faster ==

Note that with this change, serializer fields will need to be changed to getters if they are not already getters. The "build" or "watch" script will fail with an appropriate error message if this is the case.

• Enforce that serializer declarations refer to the right generated name.
• Streamline generation for classes with no fields.
• Add identical check to generated operator==.
• Make generated code compatible with strong mode implicit-dynamic:false and implicit-cast:false.

Better checking, update deps

• Add null check to generated builder "replace" methods.
• Fail with error on abstract enum classes.
• Update to build 0.7.0, build_runner 0.3.0, and build_test 0.4.0.

Support "import ... as" for field types

Merge pull request #107 from davidmorgan/release-0-5-2

Release 0.5.2.

Memoization, generics, standard JSON

• Add @memoized. Annotate getters on built_value classes with @memoized to memoize their result. That means it's computed on first access then stored in the instance.
• Support generics, in value types and in serialization.
• Add support for "standard" JSON via StandardJsonPlugin.