License fix and move

[mangin]

Changes:

1. move license to Project's root
2. add a missing sentence from 2-clause license 3-clause license ("BSD License 2.0", "Revised BSD License", "New BSD License", or "Modified BSD License"):
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Issues:

1. missing LICENSE file #47

[coveralls]

Coverage decreased (-0.1%) to 94.332% when pulling 0d5c2fc on mangin:move-license into 27cebc5 on gweis:master.

[mangin]

Hi @gweis,
I have a problem with Project's License. Your project license looks like 3-clause license ("BSD License 2.0", "Revised BSD License", "New BSD License", or "Modified BSD License"), but your license lost the last sentence:
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

So I've decided to fixed.

Could you approve this pr, please?

[hugovk]

Done in the fork at https://github.com/isodate/isodate/pull/11.