MCO-136 add .rubocop.yml from puppet
add to gemfile
(maint) quell rubocop warnings with 0.26.1

These Style/* cops moved classes to Metric/* in rubocop 0.25.0.

The current release (0.26.1) warns about it, this commit stops the
warning.
MCO-136 disable the PerceivedComplexity metric

This metric simply counts number of lines in a function body, and it's
default configuration of 7 just feels extreme.
MCO-136 enforce Style/InfiniteLoop
MCO-136 enforce Style/SpaceInsideRangeLiteral
MCO-136 disable Style/SymbolProc

Style/SymbolProc prefers

    things.map { |t| t.to_i }

be expressed as:

    things.map(&:to_i)

It's only the smallest of performance gains, but the readbility hit is real.
add rubocop target to Rakefile

Here we copy the 'rubocop' action from puppet's Rakefile
Update travis config to invoke rubocop

Here we add a dimension to the matrix to specify the check, adding the rubocop
check and excluding it from all but the rvm 2.0.0 set (as the version of ruby
we test it under is immaterial)

This is copied from puppet.
Merge pull request #258 from richardc/MCO-136-add_puppet_rubocop

MCO-136 add puppet-style rubocop rules