Add wallet manager to track wallet updates/snapshots

bfxapi/models/Wallet.py

@@ -0,0 +1,19 @@
+
+class Wallet:
+
+  def __init__(self, wType, currency, balance, unsettled_interest):
+    self.type = wType
+    self.currency = currency
+    self.balance = balance
+    self.unsettled_interest = unsettled_interest
+    self.key = "{}_{}".format(wType, currency)
+
+  def set_balance(self, data):
+    self.balance = data
+
+  def set_unsettled_interest(self, data):
+    self.unsettled_interest = data
+
+  def __str__(self):
+    return "Wallet <'{}_{}' balance='{}' unsettled='{}'>".format(
+      self.type, self.currency, self.balance, self.unsettled_interest)