Add support for multiple connections

You can now configure multiple connections like so:

    use OmniAuth::Strategies::LDAP, 
      :title => "My LDAP", 
      :host => ['10.101.10.1', '10.101.10.2'],
      :port => [389, 389],
      :method => [:plain, :plain],
      :base => ['ou=int1, dc=intridea, dc=com', 'ou=int2, dc=intridea, dc=com'],
      :uid => ['sAMAccountName', 'sAMAccountName'],
      :name_proc => [Proc.new {|name| name.gsub(/@.*$/,'')}, nil],
      :bind_dn => ['default_bind_dn', 'admin@intridea.com'],
      # Or, alternatively:
      #:filter => ['(&(uid=%{username})(memberOf=cn=myapp-users,ou=groups,dc=example,dc=com))', nil]
      :password => ['password1', 'password2']

omniauth-ldap will then try each connection in order when trying to authenticate the user.

This feature allows you to search multiple domains/hosts, cases where bind_dn's exist in subtrees and multiple subtrees are needed.