Update default Scoverage compiler plugin version

[travisbrown]

The 1.5.0 release of the plugin isn't yet synced to Maven Central, but I just tried depending on the Sonatype releases version, and it seems that I still have to set the coverageScalacPluginVersion or I get the snapshot.

This PR fixes this by updating the default version. /cc @gslowikowski

[gslowikowski]

Great, it ends this way, when I hurry.

[travisbrown]

@gslowikowski No worries, it's easy enough to work around. 😄 Thanks again!

[travisbrown]

One other issue, though—the Scoverage runtime doesn't seem to be published for Scala.js on Scala 2.11 (which is causing this PR to fail). It's available for all other version crosses.

It doesn't look like this is just a Maven Central syncing issue, since it's not on Sonatype releases either.

[gslowikowski]

I see it, this is different issue. With sbt-release this time. I've had network problems, but the release process finished successfully. Now I see java.net.ConnectionException in the log. I will push missing files to Maven central and file bug report for sbt-release plugin.

[gslowikowski]

Thank you @travisbrown for spotting the problems. You saved my life. Everything is fixed and synced now.