Improve the test for change events when calling fill_in.

  - Assert that the event is triggered.
  - Assert that the value of the input is correct at the time the event
    is triggered.
  - Do not allow multiple events to be fired for a single change.
Specify :match => :one explicitly.
textareas with linefeeds - Fixes #1068
refactor textarea document manipulation into one place
Avoid NoMethodError when calling Capybara::Selenium::Driver#quit and driver was not started
Expose execute_script to SESSION_METHODS
Link to template in contributing guide
Remove `require 'capybara/dsl'` from cucumber.rb

This file is already required in capybara.rb
Make sure multiple empty files are sent as nil, and not the empty string

Disproves #1108
Merge pull request #1104 from abotalov/expose_execute_script

Expose execute_script to SESSION_METHODS
test for within frame and scope resetting
reset scope when switching frames and windows - fixes Issue 1103
Merge pull request #1110 from twalpole/iframe

Push nil scope when switching windows and frames to fix issue 1103
support :wait option in `assert_selector` and `has_text?` matcher

closes #1105
Merge pull request #1111 from nashby/issue-1105

support :wait option in `assert_selector` and `has_text?` mather
Merge pull request #1069 from twalpole/textare_newline

Textarea with linefeeds - Fixes #1068
Permit nested features
Merge pull request #1113 from tgaff/tg/nested_features

Permit nested features
Make Rspec 3 compliant

Change explicit use of `example` variable to using the block value that
is passed in to examples and before/after hooks.
Correct reference to wrong block variable name