Update release script for _2.10 tagging convention

Author: retronym

release.sh

@@ -27,8 +27,8 @@ sbt $RELEASE
 
 cat <<EOM
 Released! For non-snapshot releases:
- - tag: git tag -s -a v$VERSION -m "scala-async $VERSION"
- - push tag: git push origin v$VERSION
+ - tag: git tag -s -a v$VERSION_2.10 -m "scala-async $VERSION for Scala 2.10"
+ - push tag: git push origin v$VERSION_2.10
  - close and release the staging repository: https://oss.sonatype.org
  - change the version number in build.sbt to a suitable -SNAPSHOT version
 EOM