Enhanced event definitions

[bryannaegele]

Add support for enhanced definitions similar to https://github.com/keathley/finch/blob/master/lib/finch/telemetry.ex by accepting a proplist of [{atom | binary, binary}] in place of a string and formatting accordingly. This should be fairly straightforward to implement.

[hauleth]

I was thinking about it, and I think that maybe it would be better to split library into two:

• Event registration
• Event extractor

This should make the migrations easier. The main problem I can see is versioning there, as one library using older version of registrator can cause downgrade in whole project.

However I thin that the API should probably use map (as it is required by telemetry anyway) and the values of such map should be atom() | {atom(), list()} | {module(), atom(), list()} so this would allow using full type specs (it could be formatted later to the expected values in format_event/1 function or whatever other user would like to have.

For user convenience we could do the translation in the Elixir macros and provide parse transform for Erlang libraries (unfortunately other languages would be on their own there).