scapy/arch refactoring

Replacing | with or

Useless line break

Fix TCP & UDP checksums when IP layer has options

Don't use /bin/bash in run_tests

Issue #110 fixes

Accept SCAPY_HISTFILE env var to set scapy hitory file (fixes #103)

python --version may output to stderr (fixes #101)

Reported by Runa Barik on Scapy ML.

Sniff can accept a list of interfaces (+ fixed bug)

Move get_if() to scapy/arch/common.py

Pad packet when needed

Update IANA Router Alert Options

Signed-off-by: Walinton Cambronero <walinton.cambronero@hpe.com>

Add section about "contributions wanted"

Sniff() optionally accepts an interface or a list of interfaces

Added "direction" attribute to pkt when received by L2ListenSocket

Patch PEP08'ified

Do not force to print interface

Updated usage.rst with multi-interfaces sniffing

Fixed missing pic in usage.rst

tethereal -> tshark

fix unicode problem for IPField

Update scripts to call python2 instead of python

Update ls() to display more info about enum fields

Packet.getlayer() method can work with string layer name

add TCP User Timeout Option (RFC 5482)

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

Allow L2pcapListenSocket to return None if where is no packets (issue #74)