Give a positive alternative to reduntant begin/rescue/end blocks

People who use the redundant syntax probably do not know the correct alternative,
so suggest the correct form in the documentation.
Merge pull request #1331 from nilbus/reduntant-block-docs

Give a positive alternative to reduntant begin/rescue/end blocks
Add more style guide references to cops

Related to #824.
Merge pull request #1336 from yous/patch-explanation

Add more style guide references to cops
Use default RSpec pattern

See
https://github.com/rspec/rspec-core/commit/667a4ca00f50fddb3fca7cdfcaf97633ba267b1f#commitcomment-7725799.

'spec/**/*_spec.rb' is compatible with default value. See
https://github.com/rspec/rspec-core/blob/v3.1.2/lib/rspec/core/rake_task.rb#L17.
Merge pull request #1333 from yous/patch-rspec

Fix spec pattern for RSpec 3.1.0
[Fix #1339] Handle eql? and equal? in OpMethod
Fix a typo
Code style
Restrict valid schemes for LineLength/AllowURI

Per #1335, #1297, the existing way of matching URIs was too permissive
and allowed a lot of lines with URI-like content (e.g. Ruby namespaces)
to be ignored by the LineLength cop.

To work around this, a whitelist of schemes will stop the vast majority
of false positives.

URISchemes was added as a configuration option for flexibility.

Closes #1335

Fixed some missing test coverage that resulted from the above changes.
The configurable URISchemes caused an existing test to miss the line of
code it should have covered.
[Fix #1340] Handle call with no receiver correctly

For blocks with an unused argument which call a method with no explicit
receiver, the Style/SymbolProc would attempt to check 'receiver.type'
and crash because receiver is nil.
Merge pull request #1338 from smangelsdorf/restrict-uri-schemes-for-line-length-cop

Restrict valid schemes for LineLength/AllowURI
Merge pull request #1341 from smangelsdorf/symbol-proc-crash

[Fix #1340] Handle call with no receiver correctly in Style/SymbolProc cop
Cut 0.26.1
Organize spec helper
Clean up copied & pasted code in HTMLFormatter and the spec

They were just copied & pasted from JSONFormatter and the HTML output
was actually not tested.
Use the same color scheme with other formatters

* Convention, Refactor - yellow
* Warning - mazenta
* Error, Fatal - red
Highlight code with markup rather than the primitive clang-style text
Markup code snippets in offense messages
Improve wording