Fix tests for non-USA culture, fix build on OSX

* Add build.sh for OSX
* Updata NUnit.TestRunners to 2..3 because 2.6.2 had a bug on OSX
* The dates need to be parsed in a consistent culture. After this, Deedle.Tests run clean for me on OSX
* Fix directory path for OSX. After this Deedle.Tests.CSharp run clean for me on OSX