Add cache for pip

Author: whtsky

.travis.yml

@@ -1,4 +1,6 @@
 language: python
+cache: pip
+
 python:
  - 2.6
  - 2.7
@@ -18,6 +20,5 @@ deploy:
   password:
     secure: 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
   on:
-    tags: true
     distributions: "sdist bdist_wheel"
     repo: whtsky/bencoder.pyx