Update README to point out 2 caveats with scopes and

provide Gemfile info for using branches.

Minor example code change.

[skip ci]
Revert "Update README to point out 2 caveats with scopes and"

This reverts commit cde3e0e6f2bf4dcf65d27f06f202c82ae57ea100.
Update README to point out 2 caveats with Scopes and

provide Gemfile info for using branches.

Minor example code change.

[skip ci]
Merge pull request #438 from caleb/multiple-fields-sort-link

Add multiple sort field support in sort_link [skip ci]
Follow-up to #438, green tests for Rails 3.1 / 3.2
Improve scopes documentation in README

[skip ci]
Update Change Log: multiple sort fields [skip ci]
Follow-up to last commit [skip ci]
Helpers::FormHelper: clean up, extract method, rename.
Memoize repeated Hash === conditional
Reduce object allocations and speed up Ransack by

extracting commonly used strings into top level Ransack
constants.
Reduce object allocations in Ransack::Nodes::Sort

`try` allocates an array on every call; we should avoid calling
it in hotspots.
Add more examples of sort_link to README [skip ci]

Added an example of sorting on multiple fields with `sort_link`
Merge pull request #439 from caleb/multi-sort-link-readme

Add more examples of sort_link to README [skip ci]
Update Change Log [skip ci]
Merge branch 'master' of https://github.com/activerecord-hackery/ransack
Update README about new sort_link features

and improve/simplify the first examples.

[skip ci]
Simplify sort_link code examples in README docs.

[skip ci]
Allow tests to run on Windows

Windows does not natively supply timezone info.
Install the tzinfo-data gem for Windows platforms.
Merge pull request #440 from asilano/master

Add 'tzinfo-data' to Gemfile for Windows environments, to help tests run on Windows