add gas limit chart

lib/history.js

@@ -436,6 +436,25 @@ History.prototype.getBlockTimes = function()
 	return blockTimes;
 }
 
+History.prototype.getGasLimit = function()
+{
+	var gasLimitHistory = _( this._items )
+		.sortByOrder( 'height', false )
+		.filter(function (item)
+		{
+			return item.block.trusted;
+		})
+		.slice(0, MAX_BINS)
+		.reverse()
+		.map(function (item)
+		{
+			return item.block.gasLimit;
+		})
+		.value();
+
+	return gasLimitHistory;
+}
+
 History.prototype.getDifficulty = function()
 {
 	var difficultyHistory = _( this._items )
@@ -570,6 +589,7 @@ History.prototype.getCharts = function()
 					uncles: item.block.uncles.length,
 					transactions: item.block.transactions.length,
 					gasSpending: item.block.gasUsed,
+					gasLimit: item.block.gasLimit,
 					miner: item.block.miner
 				};
 			})
@@ -583,6 +603,7 @@ History.prototype.getCharts = function()
 			uncles : _.pluck( chartHistory, 'uncles' ),
 			transactions : _.pluck( chartHistory, 'transactions' ),
 			gasSpending : _.pluck( chartHistory, 'gasSpending' ),
+			gasLimit : _.pluck( chartHistory, 'gasLimit' ),
 			miners : this.getMinersCount(),
 			propagation : this.getBlockPropagation(),
 			uncleCount : this.getUncleCount(),