Use Appraisal to make local testing with multiple Rails versions easier
Merge branch 'jruby-rails4'

Conflicts:
	.travis.yml
Allow prerelease rgeo-activerecord usage in bundler directly from git
Merge branch 'jruby-rails4'
Merge branch 'jruby-rails4'
Merge branch 'jruby-rails4'
Another try at fixing all columns being NOT NULL under JRuby and Rails 4

This replaces the approach taken in 7e2c054ef6260a25be5f34dd12aa45653dc9b85f
While it seemed like that might be a cleaner approach, it broke Rails 4
array column identification, without a super clean way to fix it. So
instead, we'll replicate how the JDBC adapter handles it.
Merge remote-tracking branch 'upstream/master' into appraisal

Conflicts:
	.travis.yml
	Gemfile
	Rakefile
	travis/ar40.gemfile
Merge branch 'jruby-rails4'

Conflicts:
	Version
	lib/active_record/connection_adapters/postgis_adapter/rails4/main_adapter.rb
	test/tc_ddl.rb
	travis/ar40.gemfile
Merge branch 'appraisal'

Conflicts:
	.travis.yml
	Rakefile
	travis/ar41.gemfile
Update appraisal gemfiles.
Fix allow failures syntax for travis to allow Rubinius failures.
Update contributing instructions to reflect Appraisal usage.