create pom example with specs2

invoke with mvn clean test
add scalatest, format pom
make all tests pass
Create a README
defect: wrong artifactId
remove residual arithmetic
red: "encode()" should "encode a list using run-length format"
green
red: "encodeModified" should "encode a list using run-length format but preserve single elements"
green
red: "decode" should "decode a run-length codified list"
green
red: "duplicate" should "duplicate the elements in a list"
green
red:  "duplicateN" should "duplicate the elements in a list any number of times"
green
refactor: prefer using more general function
red: "drop" should "Drop every Nth element from a list"
green: ... but I don't like the solution
update description