Force rebuild if `make tags` called
Change public API to use OutputStream Builder
Improve test for HTTP POST

Make one of the characters a reserved one to test urlencode. Change
server to respond by parroting back the request body.
Change sendRequest and receiveResponse signatures

Change sendRequest to only send the request headers and body. Move
processing the response header to the receiveResponse function. Adjust
receiveResponse to take a handler function to deal with both the
response headers and the returned entity body.

Major API change: bump package version number.
Update haddock documentation to new API
Merge branch 'signatures'