Give a bulk flavor to `Funnel.percolate`

`Funnel.percolate` now accepts a json object, or a list of json objets.
Because bulk api are so cool.

Signed-off-by: chatgris <jboyer@af83.com>
Add options to `Funnel.PercolatorPool`

  * `FUNNEL_POOL_SIZE`         => Number of process in percolators's pool
  * `FUNNEL_POOL_MAX_OVERFLOW` => Max number of messages in pool's
mailbox

Signed-off-by: chatgris <julien.boyer@af83.com>
Remove deadcode

Signed-off-by: chatgris <julien.boyer@af83.com>
Rewrite README

`Funnel` is not a http server anymore.

Signed-off-by: chatgris <julien.boyer@af83.com>