linter: Enable error checking linter (#766)

* golangci: Enable err checking linter to expose unchecked errors.

* gct: handle errors across the board

* gct: handle errors NOTE: Found bug in FTX (WIP)

* linter: fix issues

* ftx/exchanges: fix bug where error was being returned when setting pair management variables to an already enabled state

* bitmex: fix bug where a dangly supported asset in config danglied up the place.

* linter: fix more linter issues

* linter: fix my terrible spelling.

* currency: fix test

* exchanges: fix tests

* logger: fix test

* exchanges: fix tests

* glorious: nits

* vm: revert rm variable and instigate test

exchanges/exmo/exmo.go

@@ -336,9 +336,12 @@ func (e *EXMO) SendAuthenticatedHTTPRequest(epath exchange.URL, method, endpoint
 		vals.Set("nonce", n)
 
 		payload := vals.Encode()
-		hash := crypto.GetHMAC(crypto.HashSHA512,
+		hash, err := crypto.GetHMAC(crypto.HashSHA512,
 			[]byte(payload),
 			[]byte(e.API.Credentials.Secret))
+		if err != nil {
+			return nil, err
+		}
 
 		headers := make(map[string]string)
 		headers["Key"] = e.API.Credentials.Key

exchanges/exmo/exmo_test.go

@@ -126,7 +126,10 @@ func setFeeBuilder() *exchange.FeeBuilder {
 // TestGetFeeByTypeOfflineTradeFee logic test
 func TestGetFeeByTypeOfflineTradeFee(t *testing.T) {
 	var feeBuilder = setFeeBuilder()
-	e.GetFeeByType(feeBuilder)
+	_, err := e.GetFeeByType(feeBuilder)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if !areTestAPIKeysSet() {
 		if feeBuilder.FeeType != exchange.OfflineTradeFee {
 			t.Errorf("Expected %v, received %v", exchange.OfflineTradeFee, feeBuilder.FeeType)