Update dependency auto-changelog to ^1.8.1

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	References
auto-changelog	devDependencies	patch	^1.8.0 -> ^1.8.1	source

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Release Notes

CookPete/auto-changelog

v1.8.1

Compare Source

8 October 2018

• Fix Bitbucket compare links. #65
• Update markdownlint-cli to the latest version 🚀 #54
• Update markdownlint-cli to the latest version 🚀 #51
• Add author to fixes and merges #58
• Remove unsupported node versions from travis builds df63917
• Add timeout to URL fetching test d635a06
• Add node 6.0 to travis builds 088077e

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[codecov]

Codecov Report

Merging #13 into develop will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           develop    #13   +/-   ##
======================================
  Coverage      100%   100%           
======================================
  Files            1      1           
  Lines            1      1           
======================================
  Hits             1      1

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