Fixed match regex to support negative numbers

index.js

@@ -50,7 +50,7 @@ function parse(str) {
   if (str.length > 100) {
     return;
   }
-  var match = /^((?:\d+)?\.?\d+) *(milliseconds?|msecs?|ms|seconds?|secs?|s|minutes?|mins?|m|hours?|hrs?|h|days?|d|weeks?|w|years?|yrs?|y)?$/i.exec(
+  var match = /^((?:\d+)?\-?\d?\.?\d+) *(milliseconds?|msecs?|ms|seconds?|secs?|s|minutes?|mins?|m|hours?|hrs?|h|days?|d|weeks?|w|years?|yrs?|y)?$/i.exec(
     str
   );
   if (!match) {

tests.js

@@ -64,6 +64,12 @@ describe('ms(string)', function() {
   it('should work with numbers starting with .', function() {
     expect(ms('.5ms')).to.be(0.5);
   });
+
+  it('should work with numbers starting with -', function() {
+    expect(ms('-5')).to.be(-5);
+    expect(ms('-.5ms')).to.be(-0.5);
+    expect(ms('-0.5ms')).to.be(-0.5);
+  });
 });
 
 // long strings