Revert "Let Travis CI run rubocop"

This reverts commit fd2ffa5b404dfd52b21b0c1046eadc242f6d3f10.
RuboCop 0.8.2 has a bug which Syntax cop cannot be disabled.
Disable Eval cop at CaptureHelper#capture
Revert "Use rubocop 0.6.1 --no-color option instead of uncoloring colored output"

This reverts commit 5a0bca51a175948f517116126d5b2741de117564.

Conflicts:
	guard-rubocop.gemspec
Force RuboCop to colorize output even though output is not TTY
Specify dependency on rubocop gem as under 0.9.0