Add Travis CI build status image to README.md.
Make build status image link to Travis CI project page.
Add tests for around using source from options, falling back to source element in the document
Add test for sourceUrl support (currently failing due to no implementation)
Add support for sourceUrl (fixes previous tests)
Add tests for both linux and window newlines to ensure same behaviour

Not sure why this only seems to affect sourceUrl and not embedded
textarea? :/
Merge pull request #108 from DanTup/master

Add support for sourceUrl in options; to allow pulling slide content from a separate file
Create DOM wrapper and rewrite tests to simplify stubbing.

Also, #108 used XMLHttpRequest directly, which works from PhantomJS but
not from Chrome (unless started with special command line argument).
XMLHttpRequest is now a mock to enable tests to run in both environments.
#107: Add blackout mode.