Time rotation example support

[cgxxv]

Hey, guys. I have spent some time for looking for some examples which rotate log files according to the time, such as daily, hourly, or may be minutely. But unfortunately I found nothing. So I made it to help the ones who wants to do so, and don't need to spend some time for this. Also this is a general requirement. Wish you love this. Thanks.

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13 out of 14 committers have signed the CLA.

:white_check_mark: jcorbin
:white_check_mark: prashantv
:white_check_mark: FMLS
:white_check_mark: abhinav
:white_check_mark: ernado
:white_check_mark: oncilla
:white_check_mark: withshubh
:white_check_mark: markusthoemmes
:white_check_mark: ash2k
:white_check_mark: dherbst
:white_check_mark: tsoslow
:white_check_mark: r-hang
:white_check_mark: genisysram
:x: 村口大白鹅

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[codecov[bot]]

Codecov Report

Merging #932 (fefb478) into master (15be647) will decrease coverage by 0.02%. The diff coverage is n/a.

:exclamation: Current head fefb478 differs from pull request most recent head 75540a9. Consider uploading reports for the commit 75540a9 to get more accurate results

@@            Coverage Diff             @@
##           master     #932      +/-   ##
==========================================
- Coverage   98.30%   98.27%   -0.03%     
==========================================
  Files          49       44       -5     
  Lines        2120     1974     -146     
==========================================
- Hits         2084     1940     -144     
+ Misses         28       27       -1     
+ Partials        8        7       -1     

Impacted Files	Coverage Δ
stacktrace.go	96.00% <0.00%> (-4.00%)	:arrow_down:
logger.go	96.19% <0.00%> (-0.34%)	:arrow_down:
level.go	100.00% <0.00%> (ø)
global.go	96.66% <0.00%> (ø)
buffer/buffer.go	100.00% <0.00%> (ø)
zapcore/field.go	100.00% <0.00%> (ø)
zapcore/level.go	100.00% <0.00%> (ø)
zapcore/encoder.go	87.09% <0.00%> (ø)
zapcore/sampler.go	100.00% <0.00%> (ø)
zapcore/json_encoder.go	100.00% <0.00%> (ø)
... and 12 more

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