don't re-test Sequel and DataMapper support across Rails versions

Since these integrations have nothing to do with Rails, it's enough for
just the main Gemfile to include the libraries.
use "debugger" gem on 1.9
replace Rake + ruby CI runner with one in bash
add `each-gemfile` script
fix Data Mapper test assertion
test against Rails 4.0.0.rc2 and Rails 4.1 (edge)
Exclude reorder for count queries.

It turns out reorder behaves differently on Rails 3.1 and requires
explicit exclude to not pollute count query with order clause.
Rails 4 compat: AR::Base.silence requires an argument
Rails 4 compat: port named scopes to new syntax

Subtle edge case bugs pop up in AR 4 when named scopes are declared with
the old syntax. This is likely a bug with AR, but work around it for now.
don't build Rails 4 against Ruby 1.8, 1.9.2
add license information to gemspec

[ci skip]
always call `html_safe` on will_paginate result

This ensures that the HTML output of `will_paginate` view helper is not
only marked safe in Rails, but in Padrino as well.
cleaner backtrace in specs
fix `assert` method in case of failure
add test that page query param will be overriden
prevent tampering with host, port, protocol

Prevents :host, :port, :protocol settings get inherited from GET query
parameters.

Fixes #285
v3.0.5
Merge remote-tracking branch 'origin/3-0-stable'

Conflicts:
	.travis.yml
	Gemfile.lock