README: Use SVG badge (cmullaparthi#168)

Release 4.4.1

Release 4.4.0 - same as 4.4 but in a format suitable for consumption …

…by hex.pm

Release 4.4 bundling in patches from the past 6 months

Version 4.3

Version 4.2.4

Version 4.2.3

Fixed links

Version 4.2.1

Release 4.2 - improvements to pipelining