Add WithCaller(), a generalized AddCaller()

[danielbprice]

Fixes #702.

[danielbprice]

FWiW I am not attached to the name SetCaller(); just give me feedback and I'll tweak it ASAP. This issue has cropped up for me several times, so i am eager to fix it.

[codecov]

Codecov Report

Merging #806 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #806   +/-   ##
=======================================
  Coverage   98.31%   98.31%           
=======================================
  Files          43       43           
  Lines        2311     2317    +6     
=======================================
+ Hits         2272     2278    +6     
  Misses         32       32           
  Partials        7        7           

Impacted Files	Coverage Δ
options.go	100.00% <100.00%> (ø)
field.go	100.00% <0.00%> (ø)
zapcore/field.go	100.00% <0.00%> (ø)

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[prashantv]

Change looks good, I'm not so sure about the name either. I think @abhinav had a preference for AddCallerDisable, but that would always be a negative version. Another alternative, EnableCaller(bool)

Neither is great, @abhinav -- what do you think?

[abhinav]

How about WithCaller(bool)? That suggests inclusion of the caller with the other fields versus "SetCaller" which suggests you're setting the caller.

[danielbprice]

Cool! AFAICT there is nothing left for me to do. But if I've missed something please let me know.

[prashantv]

Thanks for the contribution, we'll merge it in, and do a release soon.