change travis targets

Version 3.0.7

More flexibility and resilience finding diff executable.

Thanks Skye Shaw!

Version 3.0.6

VERSION 3.0.5

Improve performance when generating html output (with inline
highlighting) on long lines. Thanks Jason Barnabe!

Version 3.0.4

handle windows vs. unix line breaks consistently in html output

Issue samg#38

Version 3.0.3

Explicitly unlink tempfiles

Remove old stuff from Rakefile

Add license to gemfile

Gemspec for version 3.0.0

Version 2.0.7

Added :allow_empty_diff option
Thanks Lincoln Ritter.