Bump versions after the 2.11.0 release.

[retronym]

The release job does this dynamically, so this doesn't correct
an error. Rather, it just brings things up to date in development
mode.

Review by @gkossakowski

[gkossakowski]

You missed the .travis.yml file: https://github.com/scala/scala-partest/blob/master/.travis.yml#L5

[retronym]

@gkossakowski I've updated the travis build. I also added a workaround for scalaBinaryVersion handling. That should get pr-scala-integrate-partest working again, which is one of the two blockers PR validation for the 2.12.x branch.

[retronym]

/)
> set scalaVersion := "2.12.0-1234"
[info] Defining *:scalaVersion
[info] The new value will be used by *:allDependencies, *:ivyScala and 12 others.
[info]  Run `last` for details.
[info] Reapplying settings...
[info] Set current project to scala-partest (in build file:/Users/jason/code/scala-partest/)
> show scalaBinaryVersion
[info] 2.11.0

[gkossakowski]

LGTM