circle: Ensure correct 0.1.0 tag is used

Since we didn't get the 0.1.0 release "right" with the first tag, it
was deleted and re-created. As discussed in [1], this is a problem
with CircleCI because the "Rebuild without cache" does not clear
the source cache.

This commit implement the suggested workaround.

[1] https://discuss.circleci.com/t/clearing-the-source-cache/2771

circle.yml

@@ -13,6 +13,12 @@ dependencies:
     - ci_addons docker load-pull-save dockcross/manylinux-x64
     - ci_addons docker load-pull-save dockcross/manylinux-x86
 
+checkout:
+  post:
+    # See https://discuss.circleci.com/t/clearing-the-source-cache/2771
+    - git tag -d 0.1.0 || true
+    - git fetch origin tag 0.1.0 || true
+
 test:
   override:
      - circleci-matrix: