Bump version to 2.27

ce258562 · Tiago Peixoto · d2cde4cb · ce258562
Commit ce258562 authored Jun 28, 2018 by Tiago Peixoto
--- a/configure.ac
+++ b/configure.ac
@@ -2,7 +2,7 @@ dnl Process this file with autoconf to produce a configure script.

 dnl graph-tool package version number
 m4_define(graph_tool_version_major, 2)
-m4_define(graph_tool_version_minor, 27dev)
+m4_define(graph_tool_version_minor, 27)

 AC_INIT([graph-tool],
        [graph_tool_version_major().graph_tool_version_minor()],