Implement new WithLogLevel option

[fgrosse]

Fixes #46

[codecov]

Codecov Report

Merging #47 into master will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
+ Coverage   95.10%   95.14%   +0.03%     
==========================================
  Files          11       11              
  Lines         777      782       +5     
==========================================
+ Hits          739      744       +5     
  Misses         25       25              
  Partials       13       13              

Impacted Files	Coverage Δ
bot.go	93.93% <100.00%> (ø)
config.go	100.00% <100.00%> (ø)

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