Good news: it's 2018 and all we need is easily source-able. You will also need a screwdriver for assembly. A parts list with example parts is provided on the project page.

2nd good news: two jumper wires suffice. No need for soldering. Just use the screwdriver  (see step 1 ;)) and replicate what is seen on the image here.

• Open pedal
• connect USB extension cable to Digispark
• connect jumper wires to terminal block
• connect jumper wires to Digispark: black wire goes to GND, yellow to P2=D2 (or change the sketch in step 3)
• Close it

Now, this is what we want: every kick is a single key press (press+release) of the delete key (better: back-space, key code 0x24; yes, I am on a Mac).

// Public domain
#include "DigiKeyboard.h"

const int LEDA=0;
const int LEDB=1;
const int BUTTON=2;

void setup() {
  pinMode(BUTTON,INPUT_PULLUP);
  pinMode(LEDA,OUTPUT);
  pinMode(LEDB,OUTPUT);
}

void loop() {
  while (digitalRead(BUTTON)==HIGH) DigiKeyboard.delay(10); // <- important to have USB stuff still running in BG.
  digitalWrite(LEDA,HIGH);
  digitalWrite(LEDB,HIGH);
  DigiKeyboard.sendKeyStroke(0);
  DigiKeyboard.sendKeyStroke(0x2A);
  DigiKeyboard.delay(100);
  while (digitalRead(BUTTON)==LOW) DigiKeyboard.delay(10);
  digitalWrite(LEDA,LOW);
  digitalWrite(LEDB,LOW);
  DigiKeyboard.delay(100);
}

Some comments:

• I use quite some debouncing delays. 
• The while loop waiting for the pedal press really needs to call a DigiKeyboard.delay to make sure that USB is not stalling.

Upload using the instructions here: https://digistump.com/wiki/digispark/tutorials/connecting

Whenever you feel the need to expressively delete things, press the pedal. Gives some relief.