add '--failed-level' option
Merge pull request #896 from hiroponz/failed-level

add '--failed-level' option
[Fix #909] Handle multiple rescue clauses in SignalException
Code style
Add auto-correction to VariableInterpolation cop
[Fix #876] Deep merge hashes in configuration when overriding

Deep (recursive) merge that was removed in #347 is added back. Some special handling is added in the CollectionMethods class so that
local settings really override the default ones even though its
config parameters are deep merged. The other cop with hash config
parameters, PercentLiteralDelimiters, will also get its config deep
merged.
Merge pull request #910 from jonas054/deep_merge

[Fix #876] Deep merge hashes in configuration when overriding
[Fix #912] Handle %-delimited string literals in LineEndConcatenation
[#912] Handle top-level constant resolution in DeprecatedClassMethods
DRY
[Fix #914] Change a two-line constant that was breaking rdoc's parsing
`FileName` accepts multiple extensions.
Merge pull request #913 from tamird/master

`FileName` should accept multiple extensions
Make --only enable the given cop

It was said in #900 that it is a bug for --only to not enable the cop.
Merge pull request #915 from jonas054/improve_only_option

Make --only enable the given cop
Fix default exclusion of vendor directories

Excluding directories from a .rubocop.yml file works, but before this
fix, the setting of AllCops/Excludes in default.yml didn't have any
effect.
Merge pull request #917 from jonas054/fix_vendor_exclude

Fix default exclusion of vendor directories