Add *ln variants of methods to the SugaredLogger

[zhupeijun]

Currently zap sugared logger dose not have method like fmt.Println, this PR adding *ln variants of methods to SugaredLogger.

zap.S().Info("a", "b")
zap.S().Infoln("a", "b")
fmt.Println("a", "b")

zap Info output: ab
zap Infoln output: a b
fmt output: a b

Related issue: #889

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #1080 (b20afd6) into master (1d435ba) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1080      +/-   ##
==========================================
+ Coverage   98.30%   98.31%   +0.01%     
==========================================
  Files          49       49              
  Lines        2123     2137      +14     
==========================================
+ Hits         2087     2101      +14     
  Misses         28       28              
  Partials        8        8              

Impacted Files	Coverage Δ
sugar.go	100.00% <100.00%> (ø)

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[abhinav]

Thanks!