Change structure to only have 1 top level project name,

sjs / jvm projects are rooted at their source directories.

Which are now:
src/main/scala-sjs
and
src/main/scala-jvm

No support yet for sjs / jvm specific resources.

Signed-off-by: Ben Jackman <ben@jackman.biz>
Bye bye bintray, trying out maven central

Signed-off-by: Ben Jackman <ben@jackman.biz>