update copyright year, remove semver license

The file semver.py to which the license pertained is long gone.

Author: akhmerov

LICENSE

@@ -1,5 +1,5 @@
 Copyright (c) 2015-2016, Brian E. Granger and Jake Vanderplas
-Copyright (c) 2016, Project Jupyter Contributors
+Copyright (c) 2016-2019, Project Jupyter Contributors
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -26,10 +26,3 @@ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-
-Semver File License
-===================
-
-The semver.py file is from https://github.com/podhmo/python-semver
-which is licensed under the "MIT" license.  See the semver.py file for details.