Remove MongoDB perl driver dependency

[pgunn]

Right now we depend on MongoDB::_Link from the 1.x version of the Perl driver to manage receive() and send() for the network; write replacement code for this and remove the dependency.

This is necessary to (eventually) reimplement this whole project across a variety of programming languages.

[pgunn]

Functions to reimplement:

$conn = MongoDB::_Link->new(...)
$conn->connect()
$conn->write()
$conn->remote_connected()
$conn->read()