Fix Windows path support in error messages

Supersede tape-testing#221. Fix tape-testing#220. Generally makes tape support more kinds of stacktrace formats.

lib/test.js

@@ -217,7 +217,7 @@ Test.prototype._assert = function assert (ok, opts) {
     if (!ok) {
         var e = new Error('exception');
         var err = (e.stack || '').split('\n');
-        var dir = path.dirname(__dirname) + '/';
+        var dir = path.dirname(__dirname) + path.sep;
 
         for (var i = 0; i < err.length; i++) {
             var m = /^[^\s]*\s*\bat\s+(.+)/.exec(err[i]);
@@ -226,12 +226,12 @@ Test.prototype._assert = function assert (ok, opts) {
             }
 
             var s = m[1].split(/\s+/);
-            var filem = /(\/[^:\s]+:(\d+)(?::(\d+))?)/.exec(s[1]);
+            var filem = /((?:\/|[A-Z]:\\)[^:\s]+:(\d+)(?::(\d+))?)/.exec(s[1]);
             if (!filem) {
-                filem = /(\/[^:\s]+:(\d+)(?::(\d+))?)/.exec(s[2]);
+                filem = /((?:\/|[A-Z]:\\)[^:\s]+:(\d+)(?::(\d+))?)/.exec(s[2]);
 
                 if (!filem) {
-                    filem = /(\/[^:\s]+:(\d+)(?::(\d+))?)/.exec(s[3]);
+                    filem = /((?:\/|[A-Z]:\\)[^:\s]+:(\d+)(?::(\d+))?)/.exec(s[3]);
 
                     if (!filem) {
                         continue;