Changes from @japgolly's branch

As first mentioned in https://github.com/Duhemm/sbt-errors-summary/issues/8, on my branch I made the following changes:

• changed colours of filenames
• made most colours bold so they are more readable on black backgrounds (at least in my envs)
• in the by-filename report at the end
  • sort by filename
  • only print if more than one file
  • print total error/warning count per file
  • don’t print line numbers
  • consolidate problem ids where possible (eg. [1-4,9] instead of [1,2,3,4,9])
• print total errors and warnings

[japgolly]

Hi, I’ve made some changes just now to put back the line numbers in the summary lines at the bottom. I’ve also put the total number of errors per file on the right. It’s nice and easy to read but still not intuitive if one doesn’t know what the numbers mean…

Anyway, here’s how it looks now. WDYT?

[dwijnand]

My confusion is I thought one number was identifying the error and the other the number of occurrences in the file, rather than the line number.

Anyways, cross-linking that conversation here: https://github.com/Duhemm/sbt-errors-summary/issues/12.