add a filemunge phase

[yanick]

Because in my case I want to change the file as it is in zilla,
not the file on disk.

[codecov-io]

Codecov Report

Merging #30 into master will decrease coverage by 0.62%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #30      +/-   ##
==========================================
- Coverage    92.5%   91.87%   -0.63%     
==========================================
  Files          14       14              
  Lines         200      197       -3     
  Branches       27       26       -1     
==========================================
- Hits          185      181       -4     
  Misses          2        2              
- Partials       13       14       +1

Impacted Files	Coverage Δ
lib/Dist/Zilla/Plugin/GitHubREADME/Badge.pm	86.36% <66.66%> (-4.95%)	⬇️
perls/5.24.1/bin/prove
perls/5.24.0/bin/prove	71.42% <0%> (ø)

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[coveralls]

Coverage decreased (-0.02%) to 98.985% when pulling 8bc7c81 on yanick:filemunge into 9e2f9ab on fayland:master.

[fayland]

thanks, will do a release shortly.

[yanick]

Thanks! You're a-maaaaah-zing!