Replace RenderFloat with FormatFloat

I suppose it was previously named RenderFloat
diff --git a/number.go b/number.go
index 6470d0d..fc422af 100644
--- a/number.go
+++ b/number.go
@@ -46,7 +46,7 @@
 // * decimal separator
 // * decimal precision
 //
-// Usage: s := RenderFloat(format, n)
+// Usage: s := FormatFloat(format, n)
 // The format parameter tells how to render the number n.
 //
 // See examples: http://play.golang.org/p/LXc1Ddm1lJ
@@ -111,7 +111,7 @@
 			//        +0000
 			if formatIndx[0] == 0 {
 				if format[formatIndx[0]] != '+' {
-					panic("RenderFloat(): invalid positive sign directive")
+					panic("FormatFloat(): invalid positive sign directive")
 				}
 				positiveStr = "+"
 				formatIndx = formatIndx[1:]
@@ -125,7 +125,7 @@
 			// 000,000.00
 			if len(formatIndx) == 2 {
 				if (formatIndx[1] - formatIndx[0]) != 4 {
-					panic("RenderFloat(): thousands separator directive must be followed by 3 digit-specifiers")
+					panic("FormatFloat(): thousands separator directive must be followed by 3 digit-specifiers")
 				}
 				thousandStr = string(format[formatIndx[0]])
 				formatIndx = formatIndx[1:]
diff --git a/number_test.go b/number_test.go
index 516f337..f4767c3 100644
--- a/number_test.go
+++ b/number_test.go
@@ -52,8 +52,8 @@
 	}
 	// Test the things that could panic
 	panictests := []TestStruct{
-		{"RenderFloat(): invalid positive sign directive", "-", 12345.6789, "12,345.68"},
-		{"RenderFloat(): thousands separator directive must be followed by 3 digit-specifiers", "0.01", 12345.6789, "12,345.68"},
+		{"FormatFloat(): invalid positive sign directive", "-", 12345.6789, "12,345.68"},
+		{"FormatFloat(): thousands separator directive must be followed by 3 digit-specifiers", "0.01", 12345.6789, "12,345.68"},
 	}
 	for _, test := range panictests {
 		didPanic := false