Change version number

Create tag for bugfix release ejabberd 2.1.12

Create tag for bugfix release ejabberd 2.1.11

Create tag for bugfix release ejabberd 3.0.0-alpha-5

Create tag for bugfix release ejabberd 2.1.10

Create tag for release ejabberd 3.0.0-alpha-4

Create tag for bugfix release ejabberd 2.1.9

Added 2.1.8 release notes.

Create tag for bugfix release ejabberd 3.0.0-alpha-3

Create tag for bugfix release ejabberd 2.1.7