If a custom header image was defined ansible was overwriting the wrong image.

also changed the way the header image tasks worked to just check if the variable equals None for it to work withtout the vagrant shared mount
checkedout max's spec-test folder and modified them to work in current environment.
to get travis working when the config.py file was owned by root. Removed the commented out part in the ansible playbook and added changing the file ownership to the travus script.
Merge pull request #670 from runasand/develop

Add instructions for yubikey setup on Tails
Merge pull request #671 from dolanjs/custom-header-image

fix custom header image
Merge pull request #672 from dolanjs/resolve-travis-config-py

remove temp travis fix for config.py
Add log file for iptables to cheat sheet
Update apt before installing packages in development
Merge pull request #673 from dolanjs/merge-max-rspec

Update Max's rspec tests for current environment. Successfully passed the

```
~/git/securedrop/spec-tests$ rspec spec
...............................................................................
Finished in 8.03 seconds
79 examples, 0 failures
```
```
spec-tests/spec/localhost/
 apache_spec.rb
 securedrop_app_spec.rb
 tor_spec.rb
```

Will need to create new roles and move the respective tests to their roles. That way the tests will be split up for the monitor server compared to the app server.
Filesystem timestamps should be UTC, regardless of system timezone
Fix formatting of singular vs. plural seconds
updated full install doc and corresponding inventory file with the IP info needed for a production install with a network firewall. With the network firewall the app server and monitor servers are on separate network segments.
Split pip requirements files into securedrop and test requirements

This is the most logical split for the pip requirements. Every
environment needs the securedrop-requirements.txt, but only environments
that need to run the tests locally (development and staging) need
test-requirements.txt.

Tested by running `vagrant up development && vagrant up /staging$/`.
Change default codename length to 7 words
Update unit test for new codename default length
added dns specific rules for postfix on the monitor server
added the uid to output rules for sending smtp
changed the hard coded port in the mon iptables rules to use the smtp_port variable instead
added IP addresses the the app and mon vm in the vagrant file
moved defining the dns IP to the environment specific yml files and removed it from the global variable yml file
add ignore statements to ossec server and agent configs.
ignore /etc/blkid.tab and /etc/apparmor.d/cache/.features
Merge pull request #674 from dolanjs/doc_ip_info

network firewall IP info update
Merge pull request #675 from freedomofpress/consolidate-pip-requirements

Split pip requirements files into securedrop and test requirements
Merge pull request #676 from freedomofpress/default-codename-length

Change default codename length to 7 words