Remove pyandoc/pandoc setup.py dependency

Fixes #21
Do not require thrift to build

In order to still support the thrift-python runtime, we'll just
ship pre-compiled versions of fb303.

Probably easier to get up and running this way
Set download_url in setup.py do github source .tar.gz
Update CHANGES for 0.2.2
Add a new build rule, "submodule_copy"

I've replaced the symlinks to externals with actual copies of the files.
The files are kept up to date automatically by developers who have the
full development environment configured (with git submodules checked out)

The submodule_copy rule takes a dictionary mapping paths in externals
to paths where the copy should reside (and stay up to date) in the
primary source.
Add optional thrift dependency in setup.py
take fmoo ver