Merge pull request #684 from Smarticles101/sieve-starter-implementation

sieve: create and validate starter implementation

exercises/sieve/src/main/java/Sieve.java

+import java.util.List;
+
+class Sieve {
+    Sieve(int maxPrime) {
+        throw new UnsupportedOperationException("Delete this statement and provide your own implementation.");
+    }
+
+    List<Integer> getPrimes() {
+        throw new UnsupportedOperationException("Delete this statement and provide your own implementation.");
+    }
+}