Improve ERB dependency detection.

The current implementation can't handle some special cases of oddly-formatted Ruby. Now we are able to detect them:

* Multi-line arguments on the `render` call
* Strings containing quotes, e.g. `"something's wrong"`
* Multiple kinds of identifiers - instance variables, class variables and globals
* Method chains as arguments for the `render` call

Also, this fix reduces the rate of "false positives" which showed up when we had calls/access to identifiers containing `render`, like `surrender` and `rendering`.
Avoid scanning multiple render calls as a single match.

Each chunk of text coming after `render` is now handled individually as a possible list of arguments.
Update changelog
setup Bundler in engines `bin/rails` stub.

This is necessary when bundling gems locally using `BUNDLE_PATH`.
Without this patch `bin/rails` fails with:

```
/Users/senny/.rbenv/versions/2.0.0-p353/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- rails/all (LoadError)
	from /Users/senny/.rbenv/versions/2.0.0-p353/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from bin/rails:7:in `<main>'
```
No need to use #send with public methods
Cleanup duplicated setup of callbacks in transactions tests
No need for instance vars on single tests
Do not set up a variable used only in two tests

Just create a local variable whenever we need the record, rather than
doing an extra find for every test on the setup method.
Move AR test classes inside the test case
Use minitest's skip rather than conditionals + early returns
Extract a method to simplify setup code
Merge pull request #13414 from britto/jb-fix-dependency-matching

Improve ERB dependency detection
Remove warning
clean up security guide: his => their [ci skip]
Merge pull request #13735 from xta/cleanup_security_guide

clean up security guide: his => their [ci skip]
Only some dynamic finders are deprecated.

find_by_* and find_by_*! are not deprecated for example, so lets add a
note only where it is needed

[ci skip]
Remove warnings on Ruby 2.1
Consistence in the block style
Fix eager load of Serializers on Active Model
set encoding to binmode for pipe