Added custom logger structure. Fix #26

[akdilsiz]

No description provided.

[bamzi]

There are many logging libraries, the zerolog might be great lib but I’m not comfortable forcing the choice at this stage.

What would a better approach be to introduce better loggings but not explicitly choosing the lib?

[akdilsiz]

The only reason why I used the zerolog lib was in order for testing. Therefore, if you like we can still use cron.Log interface to write a custom Logger without having to use any other log libraries.

As of right now, I'm currently removing zerolog, and adding a default logger as soon as I am done I will PR.

If you would like I can write the testcode while using multiple different logger libraries. What do you think?

[vgarvardt]

Almost the same can be achieved by using stdlib logger #22 - it is not structured but allows capturing all the library logs using any implementation.