Initialize Rack::Sendfile with accel mappings

Instead of requiring the X-Accel-Mapping header to be sent by nginx,
this allows separation of concerns between application and server
configuration.
Make spec_sendfile work with Ruby < 1.9
Additional Ruby 1.8 compaitiblity

Mappings are arrays of arrays to preserve order.
Define to_path on File objects in spec_sendfile.
Set TMPDIR to fix Dir.mktmpdir under jRuby
Extract Builder.new_from_string from Builder.parse_file
Add a rackup option for one-liner rack app server
Fix parsing performance for unquoted filenames

Special thanks to Paul Rogers & Eric Wong

Conflicts:
	test/spec_multipart.rb
master is now Rack 1.5, SPEC 1.2.
Merge pull request #480 from udzura/master

Add a rackup option for a one-liner rack app server
Straw man for rack.hijack*, connection hijacking!
Add straw man for the after-headers hijack
Add default port to webrick
Merge pull request #482 from oscardelben/fix_webrick_port

Add default port to webrick
Add todays releases to the README
Add missing release section from 1.1 branch
Update release date from rack-1.3 branch
Remove reference to dead link
Merge pull request #483 from oscardelben/update_readme

Remove reference to dead link
Update Lobster example
Merge pull request #484 from oscardelben/update_examples

Update Lobster example