Replace Math with FastMath for improved performance.

FastMath is a drop in replacement for the native Java math class with improved performance and fall backs to the native Java math class if necessary.

https://commons.apache.org/proper/commons-math/javadocs/api-3.3/org/apache/commons/math3/util/FastMath.html

This requires further testing and might cause chunk borders due the FastMath giving slightly different results than the native Java math class.

I also added .idea/Terra.iml to the .gitignore

src/main/java/com/dfsek/terra/util/structure/RotationUtil.java

@@ -2,6 +2,7 @@ package com.dfsek.terra.util.structure;
 
 import com.dfsek.terra.procgen.math.Vector2;
 import com.dfsek.terra.structure.Rotation;
+import org.apache.commons.math3.util.FastMath;
 import org.bukkit.block.BlockFace;
 import org.bukkit.block.data.BlockData;
 import org.bukkit.block.data.Directional;
@@ -107,7 +108,7 @@ public final class RotationUtil {
      * @return BlockFace represented by integer.
      */
     public static BlockFace fromRotation(int r) {
-        switch(Math.floorMod(r, 16)) {
+        switch(FastMath.floorMod(r, 16)) {
             case 0:
                 return BlockFace.NORTH;
             case 1: