Merge pull request #30 from Lewix/inferany

Rule for inferences of Any
Rule for Inaccessible

Warn when defining publicly overridable methods which reference private types.
Move NullaryUnit to core
Documentation for NullaryOverride
Move PrivateShadow to core
Document PrivateShadow
Rule for PrivateShadow

Addresses the issue in https://issues.scala-lang.org/browse/SI-4762.
Relevant Xlint code is at https://github.com/scala/scala/blob/2.11.x/src/compiler/scala/tools/nsc/typechecker/SuperAccessors.scala#L262
Merge remote-tracking branch 'scala/master'
Merge remote-tracking branch 'origin/privateshadow'

Conflicts:
	rules/core/src/main/scala/com/typesafe/abide/core/PrivateShadow.scala
	wiki/core-rules.md
Merge remote-tracking branch 'origin/inaccessible'

Conflicts:
	rules/core/src/main/scala/com/typesafe/abide/core/Inaccessible.scala
	wiki/core-rules.md