liblas test

Add a simple (bad) test for liblas. Per https://github.com/Homebrew/homebrew/wiki/Formula-Cookbook#add-a-test-to-the-formula, a `foo --version` style test is inferior to a functional test, but since finding or grabbing or creating a lasfile is non-trivial, it is arguable that a `--version` test is ok here (or at least better than no test).

Users can `brew install liblas --with-test` to run liblas's internal tests after building to run the library's internal tests.

Note that Homebrew is currently building liblas at version 1.7.0, which is [broken](https://github.com/libLAS/libLAS/issues/33#issuecomment-39771404), though a version bump has been requested in libLAS/libLAS#35. `brew install liblas --HEAD` should work ok.