Improve the travis-ci configurations

[GoogleCodeExporter]

I would like to reflect the latest improvements to travis-ci environments for 
our builds of DaisyReader and daisy-engine. The builds should take less time to 
complete and run more tests cleanly. There's also an ongoing need to revise the 
scripts as the Android SDK and tools are revised by Google. 

Work to do includes:
- Revise both the travis-ci build configurations as per the recent comments in 
https://github.com/travis-ci/travis-worker/issues/56

Links
- https://travis-ci.org/julianharty/daisy-engine 
- https://travis-ci.org/julianharty/new-android-daisy-reader

Original issue reported on code.google.com by julianharty on 16 Aug 2013 at 11:24

[GoogleCodeExporter]

Here's some info on travis as a package we can run locally. Useful for working 
with travis-ci 
http://about.travis-ci.org/blog/2013-07-30-new-deployment-features-and-command-l
ine-goodness/

Original comment by julianharty on 22 Aug 2013 at 11:24