Merge pull request #18 from tgarc/master

revert PR9; add --no-deps to pip wheel

Revert PR9; it was never actually needed in the first place it just fixed an
issue by side effect.

1) add --no-deps to pip wheel step in order to avoid building wheels for
   dependencies. This also addresses the issues raised in PR #11.

2) Modify the pip install step across platforms to allow installation of
   dependencies from the index. (This is required since we will no longer be
   building wheels for dependencies).

cibuildwheel/__main__.py

@@ -107,6 +107,9 @@ def main():
 
     print_preamble(platform, build_options)
 
+    if not os.path.exists(output_dir):
+        os.mkdir(output_dir)
+
     if platform == 'linux':
         cibuildwheel.linux.build(**build_options)
     elif platform == 'windows':