Block: Fixed naming, and removed internal use property from doc.

docs/Block.md

@@ -14,7 +14,6 @@ assert(block.validMerkleRoot());
 assert(block.magicnum);
 assert(block.size);
 assert(block.header); // an instance of block header, more info below
-assert(block.txsvi);
 assert(block.txs); // an array of transactions, more info below
 
 ```
@@ -49,8 +48,8 @@ For more information about the specific properties of a block header please visi
 The set of transactions in a block is an array of instances of [Transaction](Transaction.md) and can be explored by iterating on the block's `transactions` member.
 
 ```javascript
-for (var i in block.transactions) {
+for (var i in block.txs) {
-  var transaction = block.transactions[i];
+  var transaction = block.txs[i];
 }
 ```