Healthcheck options

[ryansmithevans]

Added healthcheck options and tests.
Updated Readme

[codecov-io]

Codecov Report

Merging #108 into master will increase coverage by 0.81%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #108      +/-   ##
============================================
+ Coverage     58.08%   58.89%   +0.81%     
- Complexity       79       85       +6     
============================================
  Files             9        9              
  Lines           303      309       +6     
  Branches         24       24              
============================================
+ Hits            176      182       +6     
  Misses          116      116              
  Partials         11       11

Impacted Files	Coverage Δ	Complexity Δ
...mode/gradle/plugins/docker/image/Dockerfile.groovy	70.27% <100%> (+1.25%)	25 <3> (+3)	⬆️
...adle/plugins/docker/LegacyDockerfileMethods.groovy	52.38% <100%> (+7.93%)	10 <3> (+3)	⬆️

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[ryansmithevans]

Nobody going to review this?

[ryansmithevans]

Updated to make dockerfile syntax a bit more predictable