Change AppConfig :report_page_size to :report_page_layout

* The AppConfig[:report_page_size] config variable was not used.
* Change AbstractReport#orientation method to AbstractReport#layout.
* AbstractReport#layout now returns AppConfig[:report_page_layout]
* Add a few extra comments to config-defaults.rb for info.
Merge pull request #13 from anarchivist/report-layout

Change AppConfig :report_page_size to :report_page_layout
Parallelize Travis suite

Runs dist task, unit/integration tests, and Selenium tests as three
separate suites. We were often running into timeouts before because
of Travis-CI's hard 50-minute cap.

Also make setting some of the environment variables a bit cleaner:
INTEGRATION_LOG_FILE, SCREENSHOT_ON_ERROR, and JAVA_OPTS (used to
pass the MySQL JDBC connection string).
Merge pull request #14 from anarchivist/parallelize-travis-once-and-for-all

Parallelize Travis suite
Add prefix to ensure ref_ids are valid in EAD
EAD export: only add <address> tag if there is an address
EAD export: revise extent mapping and handle empty component IDs
EAD import: map physdesc only to Extent, not to Notes
EAD export: don't insert <ref/> when reference_text is empty
Merge pull request #15 from anarchivist/ead-export-tweaks

EAD import/export tweaks (thanks to Mark Custer for feedback)