add some convenience methods to place orders

src/main/java/com/bitso/Bitso.java

@@ -390,9 +390,69 @@ public BitsoOrder[] lookupOrders(String... ordersId)
         return orders;
     }
 
+    /** Place a market order to sell the specified amount.
+     * @param book The trading pair for this order.
+     * @param amount The amount to sell, in major currency.
+     * @return The generated order ID.
+     */
+    public String placeMarketSellOrder(String book, BigDecimal amount)
+            throws BitsoAPIException, BitsoPayloadException, BitsoServerException {
+        return placeOrder(book, BitsoOrder.SIDE.SELL, BitsoOrder.TYPE.MARKET, amount, null, null, null);
+    }
+
+    /** Place a market order to buy the specified value.
+     * @param book The trading pair for this order.
+     * @param value The value to buy, in minor currency.
+     */
+    public String placeMarketBuyOrder(String book, BigDecimal value)
+            throws BitsoAPIException, BitsoPayloadException, BitsoServerException {
+        return placeOrder(book, BitsoOrder.SIDE.SELL, BitsoOrder.TYPE.MARKET, null, value, null, null);
+    }
+
+    /** Place a limit order.
+     * @param book The trading pair for this order.
+     * @param side Buy or sell
+     * @param major The amount to buy or sell, in major currency.
+     * @param minor The value to buy or sell, in minor currency.
+     * @param price The maximum price at which to buy, or minimum price at which to sell,
+     *              expressed in minor currency.
+     * @param tif The time-in-force attribute.
+     */
+    public String placeLimitOrder(String book, BitsoOrder.SIDE side, BigDecimal major, BigDecimal minor,
+                                  BigDecimal price, BitsoOrder.TIME_IN_FORCE tif)
+            throws BitsoAPIException, BitsoPayloadException, BitsoServerException {
+        return placeOrder(book, side, BitsoOrder.TYPE.LIMIT, major, minor, price, tif);
+    }
+
+    /** Place an order, using GOODTILLCANCELLED.
+     * @param book The trading pair for the order.
+     * @param side Whether it's a buy or sell order.
+     * @param type A limit or market order.
+     * @param major The amount of the order, in major currency.
+     * @param minor The value of the order, in minor currency.
+     * @param price The price of the order, in minor currency. Use null for market orders.
+     */
     public String placeOrder(String book, BitsoOrder.SIDE side, BitsoOrder.TYPE type, BigDecimal major,
             BigDecimal minor, BigDecimal price)
             throws BitsoAPIException, BitsoPayloadException, BitsoServerException {
+        return placeOrder(book, side, type, major, minor, price, BitsoOrder.TIME_IN_FORCE.GOODTILLCANCELLED);
+    }
+
+    /** Place an order, using the specified parameters.
+     * Only one of the major (amount) or the minor (value) must be specified.
+     *
+     * @param book The trading pair for the order.
+     * @param side Whether it's a buy or sell order.
+     * @param type A limit or market order.
+     * @param major The amount of the order, in major currency.
+     * @param minor The value of the order, in minor currency.
+     * @param price The price of the order, in minor currency. Use null for market orders.
+     * @param tif The time-in-force attribute, for limit orders.
+     * @return The order ID generated by the system.
+     */
+    public String placeOrder(String book, BitsoOrder.SIDE side, BitsoOrder.TYPE type, BigDecimal major,
+                             BigDecimal minor, BigDecimal price, BitsoOrder.TIME_IN_FORCE tif)
+            throws BitsoAPIException, BitsoPayloadException, BitsoServerException {
         String request = "/api/v3/orders";
 
         JSONObject parameters = new JSONObject();
@@ -414,6 +474,9 @@ public String placeOrder(String book, BitsoOrder.SIDE side, BitsoOrder.TYPE type
 
         if (type.equals(BitsoOrder.TYPE.LIMIT) && (price != null)) {
             parameters.put("price", price.toString());
+            if (tif != null) {
+                parameters.put("time_in_force", tif.name().toLowerCase());
+            }
         }
 
         if (major != null) {