Submit frozen to https://github.com/avelino/awesome-go

[marcelocantos]

...after #17, #24 and #25.

• Read https://github.com/avelino/awesome-go/blob/master/CONTRIBUTING.md.
• Unexport anything we don't want to make part of the interface. E.g.: BitIterator is a handy feature, but doesn't really fit the intent of the package from a user's perspective. It should either be unexported or exported from a different repo. MaskIterator is even more an internal construct.
• I'd be tempted to also park the lazy package on a branch till we decide what to do with it. Alternatively make sure the docs explain that it's WIP and might never happen (if we end up implementing laziness directly into the frozen package (which I'm still not sure is the same thing as semantic laziness).)