Merge pull request #180 from bitshares/bsip60-market-uri

Update market URI in BSIP60

bsip-0060.md

@@ -131,12 +131,20 @@ lowalpha             = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" |
 
 Market paths start with the word "market", followed by two `asset_id_or_symbol`s.
 
-Example: `market/BTS/USD`
+Example:
+* `market/BTS/USD`
+* `market/BTS_USD`
 
 ```BNF
-market_path = "market" "/" asset_id_or_symbol "/" asset_id_or_symbol
+market_path = "market" "/" asset_id_or_symbol [ "/" | "_" ] asset_id_or_symbol
 ```
 
+Note:
+the `/` character has been chosen as the most preferable separator between the assets.
+Due to historical reasons, the `_` separator had already been used in some applications
+before the first version of this document was published.
+New applications may consider supporting both for compatibility.
+
 ### Public Keys
 
 Public Key paths start with the "public_key" word, followed by `bitshares_public_key`.