Compilation fails on Elixir 1.7.0-rc.1

[Jan Fornoff]

Hi,

just to let you know: prometheus_ex (currently published version on Hex) seems to fail to compile on Elixir 1.7.0-rc.1 (OTP 20).

Might be related to elixir-lang/elixir#7309
Would love to contribute a fix but I'm not terribly familiar with what the purpose of the Macro is in prometheus_ex :-/

[Iliia Khaprov]

looks like CALLER argument just needs to be renamed.

[Jan Fornoff]

Seems to work just fine :-) I'll prepare a PR.