Issue warning when configuration contains an unrecognized name.

Check cop names and parameter names.
Fix random failure spec

This is about the random failure specs for interruption with Ctrl-C
https://travis-ci.org/bbatsov/rubocop/jobs/6877252

The specs were testing real behavior by running rubocop
as a child process. However it seems to be unstable
and also cannot be measured in coverage report.
So rewrote them to run in thread with some stubs and mocks.
#60 : Use the attr family of functions to define trivial accessors or mutators
Merge pull request #115 from zeroed/master

#60 : Use the attr family of functions to define trivial accessors or mutators.
Merge pull request #121 from yujinakayama/fix-random-failure-spec

Fix random failure spec
Merge pull request #120 from jonas054/catch_errors_in_config

Issue warning when configuration contains an unrecognized name.
Add new cop LeadingCommentSpace
Add new cop SemicolonMethodCall