Error while programming ATtiny45 - WProgram.h to Arduino.h?

Hello,

I am currently building an electric longboard based off of this tutorial: http://www.instructables.com/id/Make-Your-Own-Electric-Motorized-Longboard/.
The controller uses an ATtiny45 and while programming it, I encountered an issue. I followed this guide on programming the IC: High-Low Tech – Programming an ATtiny w/ Arduino 1.6 (or 1.0). When I run my code, I get this error:

In file included from C:\Users\olive\Documents\Arduino\ATtinyRemote2\ATtinyRemote2.ino:1:0:

C:\Users\olive\Documents\Arduino\libraries\SoftwareServo/SoftwareServo.h:4:22: fatal error: WProgram.h: No such file or directory

 #include <WProgram.h>

                      ^

compilation terminated.

exit status 1
Error compiling for board ATtiny.

I understand that I have to change the WProgram.h to Arduino.h, however, I’m not entirely sure how to do that. Here is the code I am using:

#include <SoftwareServo.h>

int potentiometer=A1;
int button1=3;
int button2=4;
int potval;
int curval;
SoftwareServo ESC;


void setup() {
  
  pinMode(potentiometer, INPUT);
  pinMode(button1, INPUT);
  pinMode(button2, INPUT);
  ESC.attach(1);
  curval=0;
  ESC.setMinimumPulse(800);
  ESC.setMaximumPulse(2000);
}

void loop() {
  
  while (digitalRead(button1)==HIGH){
  potval=analogRead(potentiometer);
  potval=map(potval,0,1023,0,180);
  
  while(curval<potval){
    potval=analogRead(potentiometer);
    potval=map(potval,0,1023,0,180);
    curval=curval+1;
    ESC.write(curval);
    SoftwareServo::refresh();
    delay(50);
    while(digitalRead(button2)==HIGH){
      ESC.write(curval);
      SoftwareServo::refresh();}}

  while(curval>potval){
    potval=analogRead(potentiometer);
    potval=map(potval,0,1023,0,180);
    curval=curval-1;
    ESC.write(curval);
    SoftwareServo::refresh();
    delay(50);
    while(digitalRead(button2)==HIGH){
      ESC.write(curval);
      SoftwareServo::refresh();}}
      
  ESC.write(curval);
  SoftwareServo::refresh();}

  potval=0; 
  while(curval>potval){
      curval=curval-1;
      ESC.write(curval);
      SoftwareServo::refresh();
      delay(50);}

  ESC.write(curval);
  SoftwareServo::refresh();}

Thanks for your help!

Open this file: C:\Users\olive\Documents\Arduino\libraries\SoftwareServo/SoftwareServo.h

On line 4, change WProgram.h to Arduino.h

It works! Thank you!