Upgrade analyzer, build and source_gen dependencies.

Merge pull request #35 from davidmorgan/release-0-1-3

Upgrade analyzer, build and source_gen dependencies. Release 0.1.4.

Generate builder if it's not written by hand.

Generate builder if it's not written by hand.
Make toString append commas for improved clarity.
Improve examples and tests.
Fix double null checking.

Refactor to objects

Internal refactoring, no visible changes.

Improve error output on failure to generate.

Merge pull request #28 from davidmorgan/better-error-messages

Improve error output on failure to generate.

Upgrade to source_gen 0.5.0.

Breaking change; see example for required changes to build.dart.

Strong mode compatibility, allow setters and factories.

Move null checks to "build" method for compatibility with Strong Mode analyzer.
Allow (and ignore) setters.
Allow custom factories on value classes.

Fix for changes to analyzer library.

Fixed for changes to analyzer library, changed pubspec to avoid future breakage.

Support @nullable for fields using builders. Fix constraints for source_gen.

Merge pull request #11 from google/version-constraints-null-builders

Support @nullable for fields using builders. Fix constraints for source_gen.

Allow static fields in value class. Allow custom setters in builder.

Merge pull request #2 from davidmorgan/minor-fixes

Allow static fields in value class. Allow custom setters in builder.

Fix error message for missing builder class. Allow non-abstract getters in value class.

Merge pull request #1 from davidmorgan/minor-fixes

Fix error message for missing builder class. Allow non-abstract getters, don't count them as fields.