bump version

NEWS

+Version 8.0
+    - add --text-width option for more flexible wrapping long strings in dialog text
+    - handle URIs in dialog text
+    - add --css option (--gtkrc marked as deprecated)
+    - lots of bug fixes
+
+    Special thanks to Dmitry Butskoy for a lots of contributions
+
 Version 7.3
     - fix parsing separator field for form dialog (thanks to Dmitry Butskoy)
     - fix handling user defined size of dialog with --width and --height arguments

configure.ac

-AC_INIT([YAD], [7.3], [https://github.com/v1cont/yad/issues/], yad, [https://github.com/v1cont/yad/])
+AC_INIT([YAD], [8.0], [https://github.com/v1cont/yad/issues/], yad, [https://github.com/v1cont/yad/])
 AC_CONFIG_AUX_DIR([build])
 
 AM_INIT_AUTOMAKE([1.11 foreign dist-xz no-dist-gzip])