Fixed negative decimals less than -10 don't work (#111)

Author: yuler

index.js

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

tests.js

@@ -71,6 +71,7 @@ describe('ms(string)', function() {
 
   it('should work with negative decimals', function() {
     expect(ms('-1.5h')).to.be(-5400000);
+    expect(ms('-10.5h')).to.be(-37800000);
   });
 
   it('should work with negative decimals starting with "."', function() {