Add storing bump info to file

[job13er]

This project uses semver, please check the scope of this pr:

• [ ] #none# - documentation fixes and/or test additions
• [ ] #patch# - backwards-compatible bug fix
• [x] #minor# - adding functionality in a backwards-compatible manner
• [ ] #major# - incompatible API change

CHANGELOG

Added

• New logging feature, which outputs information related to the bump action and the PR that caused it during a bump command. (Fixes #125)
• New maybe-cat-log.sh script to .travis to help people debug their use of the new logging feature.

Changed

• Our own .pr-bumper.json to enable the new logging feature
• Our own .travis.yml file to use the new maybe-cat-log.sh to log our generated log file contents during CI

[codecov-io]

Codecov Report

Merging #133 into master will increase coverage by 0.07%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #133      +/-   ##
==========================================
+ Coverage   94.14%   94.22%   +0.07%     
==========================================
  Files          13       13              
  Lines         734      744      +10     
  Branches       93       94       +1     
==========================================
+ Hits          691      701      +10     
  Misses         43       43

[job13er]

Approved