Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/prelude-ls/lib/Num.js

@@ -0,0 +1,130 @@
+// Generated by LiveScript 1.4.0
+var max, min, negate, abs, signum, quot, rem, div, mod, recip, pi, tau, exp, sqrt, ln, pow, sin, tan, cos, asin, acos, atan, atan2, truncate, round, ceiling, floor, isItNaN, even, odd, gcd, lcm;
+max = curry$(function(x$, y$){
+  return x$ > y$ ? x$ : y$;
+});
+min = curry$(function(x$, y$){
+  return x$ < y$ ? x$ : y$;
+});
+negate = function(x){
+  return -x;
+};
+abs = Math.abs;
+signum = function(x){
+  if (x < 0) {
+    return -1;
+  } else if (x > 0) {
+    return 1;
+  } else {
+    return 0;
+  }
+};
+quot = curry$(function(x, y){
+  return ~~(x / y);
+});
+rem = curry$(function(x$, y$){
+  return x$ % y$;
+});
+div = curry$(function(x, y){
+  return Math.floor(x / y);
+});
+mod = curry$(function(x$, y$){
+  var ref$;
+  return (((x$) % (ref$ = y$) + ref$) % ref$);
+});
+recip = (function(it){
+  return 1 / it;
+});
+pi = Math.PI;
+tau = pi * 2;
+exp = Math.exp;
+sqrt = Math.sqrt;
+ln = Math.log;
+pow = curry$(function(x$, y$){
+  return Math.pow(x$, y$);
+});
+sin = Math.sin;
+tan = Math.tan;
+cos = Math.cos;
+asin = Math.asin;
+acos = Math.acos;
+atan = Math.atan;
+atan2 = curry$(function(x, y){
+  return Math.atan2(x, y);
+});
+truncate = function(x){
+  return ~~x;
+};
+round = Math.round;
+ceiling = Math.ceil;
+floor = Math.floor;
+isItNaN = function(x){
+  return x !== x;
+};
+even = function(x){
+  return x % 2 === 0;
+};
+odd = function(x){
+  return x % 2 !== 0;
+};
+gcd = curry$(function(x, y){
+  var z;
+  x = Math.abs(x);
+  y = Math.abs(y);
+  while (y !== 0) {
+    z = x % y;
+    x = y;
+    y = z;
+  }
+  return x;
+});
+lcm = curry$(function(x, y){
+  return Math.abs(Math.floor(x / gcd(x, y) * y));
+});
+module.exports = {
+  max: max,
+  min: min,
+  negate: negate,
+  abs: abs,
+  signum: signum,
+  quot: quot,
+  rem: rem,
+  div: div,
+  mod: mod,
+  recip: recip,
+  pi: pi,
+  tau: tau,
+  exp: exp,
+  sqrt: sqrt,
+  ln: ln,
+  pow: pow,
+  sin: sin,
+  tan: tan,
+  cos: cos,
+  acos: acos,
+  asin: asin,
+  atan: atan,
+  atan2: atan2,
+  truncate: truncate,
+  round: round,
+  ceiling: ceiling,
+  floor: floor,
+  isItNaN: isItNaN,
+  even: even,
+  odd: odd,
+  gcd: gcd,
+  lcm: lcm
+};
+function curry$(f, bound){
+  var context,
+  _curry = function(args) {
+    return f.length > 1 ? function(){
+      var params = args ? args.concat() : [];
+      context = bound ? context || this : this;
+      return params.push.apply(params, arguments) <
+          f.length && arguments.length ?
+        _curry.call(context, params) : f.apply(context, params);
+    } : f;
+  };
+  return _curry();
+}