Overwrite asset option

This change to specify the parameter “overwriteArtifact” in order to allow the
plugin to delete the existing asset in the release. Useful especially
in SNAPSHOT version to always have the latest build in the preRelease.
Merge pull request #3 from emmanuelmathot/patch-1

Overwrite asset option
Update README.md
Updated mojo to support access token based authentication as well as username/password logins
Merge pull request #4 from rowanseymour/access_token

Updated mojo to support access token based authentication as well as username/password logins
Update README.md

added a paragraph about privateKey
preparing release to maven central
updated name and description
fixed pom
[maven-release-plugin] prepare release github-release-plugin-1.1.0
[maven-release-plugin] prepare for next development iteration
activated auto release
Update README.md
let release plugin release itself
this fixes issue#6

Signed-off-by: Emmanuel Mathot <emmanuel.mahot@gmail.com>
dns temporary version for sandbox

Signed-off-by: Emmanuel Mathot <emmanuel.mahot@gmail.com>