compile against scala 2.11.2 (by default)

Compiling against 2.11 didn't work for me, because scoverage 2.11 build was missing. I received the following error:

```sh
[warn] 	::::::::::::::::::::::::::::::::::::::::::::::
[warn] 	::          UNRESOLVED DEPENDENCIES         ::
[warn] 	::::::::::::::::::::::::::::::::::::::::::::::
[warn] 	:: com.sksamuel.scoverage#scalac-scoverage-plugin_2.11;0.95.7: not foun
```

This pull request updates scoverage to the latest version, and resolves this issue.

Update to scoverage plugin version with 2.11 build