Can't build on Linux

[CharliePoole]

The project for the extension has a post-build step that copies files to create a "pseudo-package" install so we can run integration tests. That step contains Windows paths that break the build on Linux. We'll have to find some other way to do it either by invoking a script that works on both environments or limiting the integration tests to the command-line builds that use Cake. For now, the Travis CI build is turned off.

[CharliePoole]

@ChrisMaddock I'll take a look at this one. If we can't build it on Linux, however, it is not a great loss.