Test for CURLOPT_POSTFIELDS lifecycle.

libcurl does not copy POSTFIELDS data, therefore pycurl must keep
that data around until the request finishes.
The memory is no longer allocated (c031f4591b99a7ed3c05e8ef3e11cb7814014df5)
Keep a reference to the object used for CURLOPT_POSTFIELDS.

Fixes #34
Update changelog
Break out postfields object into its own memory scope
Zap for safety
Merge pull request #35 from p-push/string-options-copies

Increment reference to CURLOPT_POSTFIELDS object
Use constants for memory groups
Merge pull request #36 from p-push/symbolic-memory-groups

Use constants for memory groups
Use util_curl_xdecref for decrementing postfields object reference count
Merge pull request #37 from p-push/util-xdecref

Use util_curl_xdecref for decrementing postfields object reference count
Update version numbers for 7.19.0.2
Update www docs
Update release process doc
Rst syntax
Rst syntax
Fix numbering
Merge pull request #38 from p-push/release-process

Update release process doc