Writable API.
Add support for returning clauses.
Merge branch 'master' into writable_fdw
Fix insert and delete for fsfdw.
Merge branch 'master' into writable_fdw
Merge branch 'master' into writable_fdw

Conflicts:
	src/python.c
Merge branch 'master' into writable_fdw
Merge branch 'master' into writable_fdw
Merge branch 'master' into writable_fdw
Transaction aware filesystem.
Add a "detail" parameter to the error reporting function.
Polish fsfdw.
Add tests for the fsfdw, and fix some bugs.
Pep8
Add small test case and bugfix for successive updates to "content".
Disable buffering on write.
Move the xact callback to a 9.3-only guarded code.
Only aquire READ-ONLY lock when nothing else is necessary.
Merge branch 'master' into writable_fdw

Conflicts:
	src/python.c
Python3 support.