allow Protobuf::Message based classes to be inherited

[skippy]

addresses #246

NOTE:

I wrapped most of the methods in Protobuf::Message::Fields in ClassMethods to keep it clearer about what is going where. If you view the diff in github without whitespace changes you'll see the minimal changes to that class.

[skippy]

see non-whitespace changes

[skippy]

hmm... looks like a timing error on a test

[skippy]

I should have said 'looks like a timing error on a [non-related] test'. I suspect if you kick travis to re-run the tests things will run just fine.

[localshred]

K, will do (thanks for the ping :)).

[localshred]

Now it's failing due to formatting issues (rubocop) https://travis-ci.org/localshred/protobuf/jobs/49230691

[skippy]

hey @localshred ; very odd. when I run bundle exec rake locally it runs with no errors (using ruby 2.2, 2.1.5, 2.1, and 2.0.0-p598 on osx 10.10).

The rubocop errors shown in travis have nothing to do with this PR; the files flagged weren't modified by this PR. I did a quick scan and the Rakefile and .travis.yml all seem to be in order.

Any thoughts on what is going on?

[localshred]

Ya, ran your branch locally and everything seems ok. To say I'm unhappy with the state of our tests is an understatement. Thanks for the code!

[localshred]

Released under v3.4.4.

[localshred]

Finally got rubocop to shut up, tests are now passing on travis.