added description of the methods

README.md

@@ -1,4 +1,12 @@
-openexchangerates
+### openexchangerates ###
-=================
-
 Implementation API openexchangerates.org on Ruby
+
+### methods ###
+**1.** `get_latest()`  
+Get the most recent exchange rates
+
+**2.** `get_currencies`  
+get list of currency codes and names
+
+**3.** `get_old(date)` *(in development)*  
+get rates for any given day, where available