Use float instead of double to reduce the size of JsonVariant (issue #134)

include/ArduinoJson/Arduino/Print.hpp

@@ -20,6 +20,7 @@ class Print {
 
   size_t print(const char[]);
   size_t print(double, int = 2);
+  size_t print(int);
   size_t print(long);
   size_t println();
 };

include/ArduinoJson/Arduino/String.hpp

@@ -16,6 +16,7 @@ class String : public std::string {
   String(const char *cstr = "") : std::string(cstr) {}
   String(const String &str) : std::string(str) {}
   explicit String(long);
+  explicit String(int);
   explicit String(double, unsigned char decimalPlaces = 2);
 };