Use encrypted PyPI API token to authenticate with PyPI for upload

* Previously encrypted password from .travis.yml for hepdata-converter.
* This gave a failed PyPI deployment, so might be repository-specific.
* Used "travis encrypt" CLI tool to encrypt PyPI API token.

Signed-off-by: Graeme Watt <[email protected]>

.travis.yml

@@ -32,9 +32,9 @@ deploy:
   skip_cleanup: true
   skip_existing: true
   provider: pypi
-  user: hepdata
+  user: "__token__"
   password:
-    secure: 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
+    secure: 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
   distributions: "sdist bdist_wheel"
   on:
     tags: true