Merge rubygems and bundler rubocop rules

[hsbt]

What was the end-user or developer problem that led to this PR?

We have two rubocop rules between rubygems and bundler. We should move to merge them.

What is your fix for the problem, implemented in this PR?

I merge .rubocop_bundler.yml into .rubocop.yml only non-effect cops at first in this PR. After that, I'll triage rubocop_bundler.yml cops and modify rubygems or bundler files step by step.

@deivid-rodriguez @simi Do you have any concerns about this merger plan?

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags

[hsbt]

Layout/CaseIndentation and Layout/SpaceAroundOperators are conflicts on rubygems/bundler. I aligned their cops in this time.

[deivid-rodriguez]

No concerns, and I like your plan.

[hsbt]

Thanks to quick response. I'll work Layout, Style, Naming and other cops.

[simi]

💪 getting rubygems and bundler closer one step at the time 💪

Btw. I have still plan to add Naming/MemoizedInstanceVariableName, I'll postpone my PR until this is finished.

[hsbt]

I confirmed rule differences with the following way:

>> master = (Psych.load_file(".rubocop.yml").keys + Psych.load_file(".rubocop_bundler.yml").keys).uniq
# swith to this branch
>> merge = (Psych.load_file(".rubocop.yml").keys + Psych.load_file(".rubocop_bundler.yml").keys).uniq
>> merge - master
=> ["inherit_from"]
>> master - merge
=> []

There is no missing cops with this PR.