Make setup.py work when invoked from a different path.

setup.py

@@ -33,8 +33,10 @@ DEPS = {
   ),
 }
 
+_file_dirname = os.path.dirname(__file__)
+
 def download(url, filename, hexdigest):
-  filename = join('apachedex', filename)
+  filename = join(_file_dirname, 'apachedex', filename)
   if not exists(filename):
     urllib.urlretrieve(url, filename)
   if hashlib.md5(open(filename).read()).hexdigest() != hexdigest:
@@ -47,7 +49,7 @@ for filename, (url, hexdigest) in DEPS.items():
 if sys.argv[1:] == ['deps']:
   sys.exit(0)
 
-description = open('README').read()
+description = open(join(_file_dirname, 'README')).read()
 
 setup(
   name='APacheDEX',