make test suite runnable with "setup.py test"

setup.py

@@ -30,6 +30,7 @@ setup(name='beets',
       license='MIT',
       platforms='ALL',
       long_description=_read('README'),
+      test_suite='test.testall.suite',
 
       packages=[
           'beets',

test/__init__.py

@@ -0,0 +1,2 @@
+# placeholder
+

test/testall.py

@@ -17,14 +17,20 @@
 import unittest
 import os
 import re
+import sys
+
+pkgpath = os.path.dirname(__file__)
+sys.path.append(pkgpath)
+os.chdir(pkgpath)
 
 def suite():
     s = unittest.TestSuite()
     # get the suite() of every module in this directory begining with test_
-    for fname in os.listdir('.'):
+    for fname in os.listdir(pkgpath):
         match = re.match(r'(test_\S+)\.py$', fname)
         if match:
-            s.addTest(__import__(match.group(1)).suite())
+            modname = match.group(1)
+            s.addTest(__import__(modname).suite())
     return s
 
 if __name__ == '__main__':