support Access-Control-Request-Headers
cleaned up
got rid of unnecessary .get call
Send an explicit Content-Length header with /drip/

It's useful for testing tools which track the progress of a request to know
the content length ahead of time.

Test included. I've verified that the new tests do fail without this change,
response.content_length is None if an explicit Content-Length isn't set.
Show way to run httpbin as a python module.

It's already there, may as well mention how to run httpbin without gunicorn.
Imports; remove dup base64, alpha sort
GH-162: No 500 w/ better handle missing dict keys
GH-125: Support multiple headers with same key

Fixes: GH-125
move tracking scripts into separate file
add runscope trackign
Update repository URL in app.json

Fixes #174
Merge pull request #175 from sigmavirus24/patch-1

Update repository URL in app.json
Update Readme for Deploy to Heroku button fix
Merge pull request #176 from mrkd/master

Update Readme for Deploy to Heroku button fix
Update httpbin.1.html
Merge pull request #170 from msabramo/patch-1

Imports; remove dup base64, alpha sort
Merge pull request #172 from msabramo/GH-125

GH-125: Support multiple headers with same key
Merge pull request #177 from mrkd/master

Update template to fix deploy to Heroku button
Merge pull request #171 from msabramo/GH-162

GH-162: No 500 w/ better handle missing dict keys
Merge branch 'master' of github.com:Runscope/httpbin