ImportsChecker: fix lexicographic sort for groups

[kitbellew]

Lexicographic imports sorting used in IDEs (Intellij, Eclipse) considers
the entire import string.

However, for groups, only the part preceding the group was passed into
the comparison method, not taking into account the opening curly brace
and the symbol following it. Let's add them to get the right behaviour.

A follow-up to pull request #234.

[codecov-io]

Codecov Report

Merging #349 into master will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff          @@
##           master   #349   +/-   ##
=====================================
  Coverage       0%     0%           
=====================================
  Files          62     62           
  Lines        1495   1498    +3     
  Branches      146    146           
=====================================
- Misses       1495   1498    +3

Impacted Files	Coverage Δ
...la/org/scalastyle/scalariform/ImportsChecker.scala	0% <0%> (ø)	⬆️

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[kitbellew]

@matthewfarwell can you please take another look? my previous commit, #234 2 years ago, turned out to be incomplete and leads to conflicts with IDEs when import rename is used.

[dvwilliamson]

@SethTisue It looks like you may have more recently looked at this repo. It looks like a good PR for a good repo, but no one's merged it in for a while. Trying to give my upvote for what its worth.

[SethTisue]

@dvwilliamson the action's over at @mwz's https://github.com/beautiful-scala/scalastyle

[kitbellew]

@dvwilliamson the action's over at @mwz's https://github.com/beautiful-scala/scalastyle

thanks, closing this, created beautiful-scala#188