Use literal '/'s to build internal zip file paths (#51)

* Use posixpath to build internal zip file paths

* Use literal / instead of posixpath

* Update piptool.par and whltool.par

rules_python/whl.py

diff --git a/rules_python/whl.py b/rules_python/whl.py
index c102d03..e3544d8 100644
--- a/rules_python/whl.py
+++ b/rules_python/whl.py
@@ -60,12 +60,12 @@
     with zipfile.ZipFile(self.path(), 'r') as whl:
       # first check for metadata.json
       try:
-        with whl.open(os.path.join(self._dist_info(), 'metadata.json')) as f:
+        with whl.open(self._dist_info() + '/metadata.json') as f:
           return json.loads(f.read().decode("utf-8"))
       except KeyError:
           pass
       # fall back to METADATA file (https://www.python.org/dev/peps/pep-0427/)
-      with whl.open(os.path.join(self._dist_info(), 'METADATA')) as f:
+      with whl.open(self._dist_info() + '/METADATA') as f:
         return self._parse_metadata(f.read().decode("utf-8"))
 
   def name(self):

tools/piptool.par

diff --git a/tools/piptool.par b/tools/piptool.par
index ee03cfc..206a33d 100755
--- a/tools/piptool.par
+++ b/tools/piptool.par
Binary files differ

tools/whltool.par

diff --git a/tools/whltool.par b/tools/whltool.par
index 6c06a50..fece5b0 100755
--- a/tools/whltool.par
+++ b/tools/whltool.par
Binary files differ