cert.py improvements

* Improve cert.py : independence from openssl, ECDSA support, sign/verify capabilities

* Make travis install python-ecdsa

* Clarify ECDSA support

* Cleaning up for cert.py

EAPOL / EAP updates and regression tests

* Flip conditional for simplicity
* Indent lines
* Include Travis CI build status image & link

Allow one to send the TCP User Timeout Option described in RFC 5482 in
a crafted TCP segment.
Also added unit tests in new "TCP options" section of
test/regression.uts

Insert DER test data inside x509.uts and move it from scapy/layers/ to test/ (also, remove obsolete X.509 tests from test/regression.uts

As suggested by @guedou, this adds tests for fragment() and
defragment() functions.

--HG--
branch : ICMPv6NDOptDNSSL fixes