Adds --force-exclusion option to rubocop CLI

If this option is not passed rubocop will check the files in git stage even though they are in paths excluded in the rubocop config file.
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Version bump to 0.16.1
reject also directories from staged files list, fix #147, update #149
update supported versions on travis
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Version bump to 0.16.2
Update rubocop.rb

RuboCop has changed its name from `Rubocop` to `RuboCop`.
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bump the required pluginator version, fix #129
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Version bump to 0.16.3
PreCommit now requires `rubocop` ~> 0.23

The Rubocop project changed the casing of their top level namespace
from `Rubocop` to `RuboCop`. We now have a hard dependency on this
capitalization in the code.

In order to run the test suite properly, you must have rubocop ~>
0.23 installed.
Allow debugger when it is in another context.

We only want to catch debugger when it is being used as a debugger
statement. Not when it is in commments, or quotes, or any other
intended use.
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Whatever rubocop
Allow commented out `:path` arguments in Gemfile.
add run cli command, update #153
add a note about version for run cli in README, update #153
remove extra semicolon, update #153