Add example code to Scopes docs in README

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Follow-up to last commit [skip ci]
Follow-up to last 2 commits on Scopes/Class Methods docs

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Add missing argument to Scopes example [skip ci]
README: Add missing `end` and improve explanation

in Scopes/Class Methods section.

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Merge pull request #428 from cubus/master

Add Romanian I18n. Fix attribute translations when using AR with STI.
Refactor Ransack::Translate, esp. the attribute_name

class method, hopefully for better readability and
maintainability.

All these class methods make me wonder if `attribute_name`
shouldn’t be in a separate class with instance methods
instead.
Replace Hash#compact with #reject for Rails < 4.1
Remove unneeded arg
README: Provide an alternative to `distinct: true`

for cases when the latter is causing problems while
searching on associated table's columns.

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Follow-up to previous commit [skip ci]
Update the change log [skip ci]
Make `ransackable/ransortable` methods clear/coherent

between implementation and docs.
Clarify [skip ci]
Clarify ransackable_scopes is an array of symbols.

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Clarify class methods for whitelisting in base.rb  

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Merge pull request #1 from activerecord-hackery/master

rebase ....