fix poller test

Messages received are now under the format `{PollerPid, Msg}`.
fix zauth error

czmq 2.0.3 has a small error and doesn't include platform.h:
http://permalink.gmane.org/gmane.network.zeromq.devel/23025

This change fix it by patching zauth.c and zsockopt.c as described in
the mailing-list post above.

fix #4
keep libsodium optimisations
fix readme typo
bump zeromq to 4.0.4
add a simple command to run tests in the makefile
add options to set context options

implement the following functions:

- zctx_set_iothreads/2,
- zctx_set_linger/2,
- zctx_set_pipehwm/2,
- zctx_set_sndhwm/2,
- zctx_set_rcvhwm/2,

See the manual for more informations.
add options to set context options

implement the following functions:

- zctx_set_iothreads/2,
- zctx_set_linger/2,
- zctx_set_pipehwm/2,
- zctx_set_sndhwm/2,
- zctx_set_rcvhwm/2,

See the manual for more informations.
Merge pull request #12 from benoitc/feature/czctx_fun

add options to set context options
Cleanup testing facility, add make check target