Added functional tests for ServerDetailsPlugin.
Fixed #31 test and fixed #32 header name bug for X-XSS-Protection.

In this commit, we have added a functional test for
XXSSProtectionPlugin. Furthermore, like #27, we have to read the
lower-case header name for X-XSS-Protection.

We should actually address this issue either with curly.py or
individually with each plugin. See issue #33.
Instruct travis to create dist for minion and use pip to install minion.
Instruct travis to install stunnel.
use sudo to kill on travis.
Instruct travis to start mongodb.

We were getting "ConnectionFailure: could not connect to
127.0.0.1:27017: [Errno 111] Connection refused" error in Travis.
Instruct travis to start minions.
Tells travis to create a basic plan.
Fixed #38: robots-scanner is added to setup.py
Fixed #36. Fixed #11. RobotsPlugins now use robots-scanner validator.

The robots-scanner has a very simple scanner to scan the content of
robots.txt. The overall validation in RobotsPlugins is written in the
commit (see plugins/basics.py).
Use robots-scanner 0.1.1.

robots-scanner has been updated to remove print statements from the its
source code.