Log Message:
Update thin to 1.7.0.

== 1.7.0 Dunder Mifflin
 * Rack 2 support
 * Ensure Response body.close is called in the same thread
   Fixes issues with ActiveRecord connection management [#307]
 * Fix TCP/IP Backend reports incorrect port when asked to bind to 0 [meschbach]
 * Work with ruby 2.3's --enable-frozen-string-literal [jeremyevans]