Collections API: Replace build.scala with build.sbt

[kellyi]

Per a comment on #55 we should replace the existing build.scala file with build.sbt

[rajadain]

This comment: #55 (comment)

[rajadain]

See if this also resolves these warnings:

[warn] /Users/ttuhinanshu/dev/mmwg/project/build.scala:73: `<<=` operator is deprecated. Use `key := { x.value }` or `key ~= (old => { newValue })`.
[warn] See http://www.scala-sbt.org/0.13/docs/Migrating-from-sbt-012x.html
[warn]     mergeStrategy in assembly <<= (mergeStrategy in assembly) {
[warn]                               ^
[warn] /Users/ttuhinanshu/dev/mmwg/project/build.scala:25: trait Build in package sbt is deprecated: Use .sbt format instead
[warn] object Geoprocessing extends Build {
[warn]                              ^
[warn] two warnings found

[kellyi]

We'll need to update the deployment instructions, too, since they describe changing the version number in build.scala:

https://github.com/WikiWatershed/mmw-geoprocessing#deployments