SS 3.1 compatibility + fixed Danish dates

When trying to install via Composer I got:

	richardsjoqvist/silverstripe-localdate dev-master requires silverstripe/framework 3.0.* -> satisfiable by silverstripe/framework[3.0.2.1, 3.0.3, 3.0.3-rc1, 3.0.3-rc2, 3.0.4, 3.0.5, 3.0.6, 3.0.6-rc1, 3.0.6-rc2, 3.0.7, 3.0.7-rc1, 3.0.8, 3.0.x-dev].

So I fixed it by changing the require line in your `composer.json` file.

Also the Danish translations didn't work out of the box, I had to rename them.