sbt-crossproject 0.5.0

This is mostly a simplifying release, taking advantage of the improvements that have made their way to sbt-scalanative 0.3.7 and sbt-scalajs 0.6.23.

Breaking changes

• sbt-scalajs-crossproject 0.5.0 requires sbt-scalajs >= 0.6.23 (or >= 1.0.0-M2). As a reminder, sbt-scalanative-crossproject requires sbt-scalanative >= 0.3.7 since v0.4.0.
• The result type of CrossProject.Builder.crossType has changed from CrossProject to Builder, so that it can be chained with further Builder methods such as withoutSuffixFor (#93). This is usually not an issue as there is an implicit conversion from CrossProject.Builder to CrossProject. However, if you happen to directly assign the result of crossType() to a lazy val foo = ..., without subsequent calls to .settings(), and without an explicit type like : CrossProject, your build might cease to properly function. You can fix this with an explicit call to .build() or with an explicit : CrossProject.
• All the APIs that were deprecated since v0.3.0 have been removed.