fixed "must not be in the source directory"

lib/jscover.js

@@ -34,9 +34,15 @@ module.exports = function jscover(source, target, options, callback) {
   target = target || '';
   options = options || [];
   var tmpName = '__cov__' + Date.now();
-  var tmpTargetDir = path.join(path.dirname(target), tmpName);
+  var tmpdir = process.env.TMPDIR || '/tmp';
+  var tmpTargetDir = path.join(tmpdir, tmpName);
   var tmpTarget = path.join(tmpTargetDir, path.basename(target));
 
+  var cleanup = function () {
+    fse.removeSync(tmpTargetDir);
+    fse.removeSync(path.join(target, tmpName));
+  };
+
   var cmd = JSCoverCommand;
   if (options && options.length > 0) {
     cmd += ' ' + options.join(' ');
@@ -59,6 +65,7 @@ module.exports = function jscover(source, target, options, callback) {
     }
     if (err) {
       debug(err, stderr);
+      cleanup();
       return callback(err, output);
     }
 
@@ -88,10 +95,10 @@ module.exports = function jscover(source, target, options, callback) {
         }
       }
     }, function end() {
-      fse.removeSync(tmpTargetDir);
-      fse.removeSync(path.join(target, tmpName));
+      cleanup();
       callback();
     }, function error(err, errPath) {
+      cleanup();
       console.error('%s error: %s', errPath, err);
       callback(err);
     });