Document how to require multiple keys in params

With reference to commit 735da78f6e570a076820cb0edd23e38c1837e5b2
Merge pull request #146 from josephers/patch-1

Document how to require multiple keys in params
link to the Rails guide section about strong_parameters.
Update lock file
do not break params filtering on nil values
Merge pull request #165 from nashby/rails-issue-12149

do not break params filtering on nil values
Strong parameters should permit nested number as key. Fixes Rails Issue 12293.
Merge pull request #171 from kennyj/fix_rails_issue_12293

Strong parameters should permit nested number as key. Fixes Rails Issue 12293.
Change ActionController::Parameters#require behavior when value is empty
When the value for the required key is empty an ActionController::ParameterMissing is raised which gets caught by ActionController::Base and turned into a 400 Bad Request reply with a message in the body saying the key is missing, which is misleading.

With these changes, ActionController::EmptyParameter will be raised which ActionController::Base will catch and turn into a 400 Bad Request reply with a message in the body saying the key value is empty.
Merge pull request #115 from sebasoga/change_require_behaviour

Change behavior ActionController::Parameters#require when value is empty
Revert "Merge pull request #115 from sebasoga/change_require_behaviour"

This reverts commit fd00868c49003456954bb81f187fd0430566beee, reversing
changes made to e0390559b860820d490ede47ea8c80b0e4f3c883.
Improve wording in AC::ParameterMissing error message
Updates gemfile for Rails 3.1.x and 3.2.x
Updates test to work with ruby 1.8.7

Updates a hash with the old hash syntax
Merge pull request #179 from edelpero/fixes_gemfiles

Updates gemfile for Rails 3.1.x and 3.2.x
Updates another new hash syntax to work with ruby 1.8.7
Merge pull request #180 from edelpero/fixes_test_for_old_ruby_version

Updates test to work with ruby 1.8.7
Updates Gemfile source for Rails 3.0.x according to TravisCI
Merge pull request #181 from edelpero/updates_gemfile_3_0_x

Updates Gemfile source for Rails 3.0.x according to TravisCI
Add two missing asserts in NestedParametersTest