Fix deprecation warnings.

Author: pauldoo

src/com/pauldoo/euler/common/Summations.scala

@@ -3,8 +3,8 @@ package com.pauldoo.euler.common
 object Summations {
   def sum(range: Range): BigInt = {
     // TODO: Replace with Range.sum(..) ?
-    val actualLast = range.first + range.step * (range.length - 1);
-    ((range.first + actualLast) * (range.length)) / 2;
+    val actualLast = range.head + range.step * (range.length - 1);
+    ((range.head + actualLast) * (range.length)) / 2;
   }
 
   // Sum of k^2 for k = 0 to n

src/com/pauldoo/euler/puzzle/Puzzle7.scala

@@ -4,6 +4,6 @@ import com.pauldoo.euler.common.Naturals
 
 object Puzzle7 extends Puzzle {
   def answer() = {
-    primes.drop(10000).first;
+    primes.drop(10000).head;
   }
 }

src/com/pauldoo/euler/puzzle/Puzzle9.scala

@@ -7,6 +7,6 @@ object Puzzle9 extends Puzzle {
       a <- 1 to 1000 / 3;
       b <- (a + 1) to (1000 - a - 1) / 2;
       val c = 1000 - a - b if a * a + b * b == c * c
-    ) yield a * b * c).first
+    ) yield a * b * c).head
   }
 }