Add scala 2.12.0-RC1

[ghost]

This PR adds 2.12-0-RC1 support.

Please note that makesite has been disabled due to an error in 2.12, see comments

[ghost]

Re failing build on 2.12.0-RC1 this is during tut in:

[tut] compiling: ./docs/src/main/tut/either.md
[tut] *** Error reported at ./docs/src/main/tut/either.md:239: failure was asserted but no failure occurred
doApp: scala.util.Either[Object,ServiceValue]

So this diff passes in 2.12.0-RC1 only, but is not the solution, just a helper/illustration:

@@ -235,7 +235,7 @@ object Service {
 Let's say we have an application that wants to do database things, and then take database
 values and do service things. Glancing at the types, it looks like `flatMap` will do it.

-```tut:fail:silent
+```tut:silent
 def doApp = Database.databaseThings().flatMap(Service.serviceThings)

This is all clearly due to new Either semantics in 2.12 so I'll leave this as is for now.

2.11.8 build failure looks like the old OOM issues, so I'll turn of some instrumentation as I mentioned ^^

[ghost]

Actually, the 2.11 build failure is identical to https://travis-ci.org/typelevel/cats/jobs/161257117 so I'm done here for now 😄

[magicknot]

@BennyHill you don't need to compile scoverage anymore. You can do something like this:

plugins.sbt:
addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.4.0")

build.sbt
coverageScalacPluginVersion := "1.3.0-RC1"

[travisbrown]

@magicknot Thanks! I just confirmed locally that that works.

[ghost]

I know - I did most of the changes for scoverage along with @paulp 😄

[ghost]

But we do need the more recent sbt plugin as well, 1.5.0-RC1 and so I will use that too.

[codecov-io]

Current coverage is 91.84% (diff: 100%)

Merging #1382 into master will increase coverage by 0.15%

@@             master      #1382   diff @@
==========================================
  Files           240        240          
  Lines          3610       3567    -43   
  Methods        3546       3500    -46   
  Messages          0          0          
  Branches         63         67     +4   
==========================================
- Hits           3310       3276    -34   
+ Misses          300        291     -9   
  Partials          0          0          

Powered by Codecov. Last update a392654...409e39e

[ghost]

Todo: Add new issue with makesite error once this is in, with notes on how to replicate. Also add new issue to reintroduce makesite, either in full with fix or partial, excluding 2.12

[ghost]

Ref two scala issues:

• https://issues.scala-lang.org/browse/SI-9923
• https://issues.scala-lang.org/browse/SI-9931

[travisbrown]

Mind if I close this, @BennyHill, since these commits are in #1415?

[ghost]

Closing since these commits are in #1415