Update version

ChangeLog.rst

-5.0.0 - TBD
------------
+5.0.0 - 2018-05-21
+------------------
 
 * Added a requirement for partial C++11 support, most importantly variadic
   templates and type traits, and dropped ``FMT_VARIADIC_*`` emulation macros.

doc/build.py

@@ -6,7 +6,7 @@ import errno, os, shutil, sys, tempfile
 from subprocess import check_call, check_output, CalledProcessError, Popen, PIPE
 from distutils.version import LooseVersion
 
-versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0']
+versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0']
 
 def pip_install(package, commit=None, **kwargs):
   "Install package using pip."