Renderer class:

package com.Nitrodev.WarehouseStorage.client.render.items;

import com.Nitrodev.WarehouseStorage.WarehouseStorage;
import com.Nitrodev.WarehouseStorage.items.ModItems;
import net.minecraft.client.Minecraft;
import net.minecraft.client.resources.model.ModelResourceLocation;
import net.minecraft.item.Item;

/**
 * Created by Jukka on 22.12.2015.
 */
public class ItemRenderRegister {

    public static String modid = WarehouseStorage.MODID;

    public static void registerItemRenderer() {
        reg(ModItems.itemPlank);
    }

    public static void reg(Item item) {
        Minecraft.getMinecraft().getRenderItem().getItemModelMesher()
                .register(ModItems.itemPlank, 0, new ModelResourceLocation(modid + ":" + item.getUnlocalizedName().substring(5)));
    }
}

Model .json file:

{
  "parent":"builtin/generated",
  "textures": {
      "layer0":"WarehouseStorage:items/item_plank.png"
  },
  "display": {
      "thirdperson": {
          "rotation": [ -90, 0, 0 ],
          "translation": [0, 1, -3 ],
          "scale": [ 0.55, 0.55, 0.55 ]
      },
      "firstperson": {
          "rotation": [ 0, -135, 25 ],
          "translation": [0, 4, 2 ],
          "scale": [ 1.7, 1.7, 1.7 ]
      }
  }
}