[Breaking] Take the *first* part of the fillStr when truncating.

Per tc39/proposal-string-pad-start-end#6, and to be consistent with Ruby and PHP.

Fixes #1.

README.md

@@ -18,7 +18,7 @@ Most common usage:
 ```js
 var padLeft = require('string.prototype.padleft');
 
-assert(padLeft('foo', 5, 'bar') === 'arfoo');
+assert(padLeft('foo', 5, 'bar') === 'bafoo');
 
 padLeft.shim();
 

implementation.js

@@ -26,7 +26,7 @@ module.exports = function padLeft(maxLength) {
 		stringFiller += fillStr;
 	}
 	if (stringFiller.length > fillLen) {
-		stringFiller = slice(stringFiller, -fillLen);
+		stringFiller = slice(stringFiller, 0, fillLen);
 	}
 
 	return stringFiller + S;

test/tests.js

@@ -5,7 +5,7 @@ module.exports = function (padLeft, t) {
 		st.equal(padLeft('a', 3, 'b'), 'bba', 'string pads left with single character');
 		st.equal(padLeft('abc', 3, 'd'), 'abc', 'string already of maximum length noops');
 		st.equal(padLeft('abc', -3, 'd'), 'abc', 'string already larger than maximum length noops');
-		st.equal(padLeft('cd', 3, 'ab'), 'bcd', 'string with maximum length equal to length plus filler length, pads');
+		st.equal(padLeft('cd', 3, 'ab'), 'acd', 'string with maximum length equal to length plus filler length, pads');
 		st.equal(padLeft('abc'), 'abc', 'absent maximum length is noop');
 		st.equal(padLeft('a', 3), '  a', 'absent fillStr defaults to a space');
 		st.equal(padLeft('ed', 6, null), 'nulled', 'non-string fillStr gets stringified');
@@ -14,7 +14,7 @@ module.exports = function (padLeft, t) {
 	});
 
 	t.test('truncated fill string', function (st) {
-		st.equal(padLeft('a', 2, 'bc'), 'ca', 'truncates at the provided max length');
+		st.equal(padLeft('a', 2, 'bc'), 'ba', 'truncates at the provided max length');
 
 		st.end();
 	});