Build all branches, cache Conan downloads.

appveyor.yml

@@ -1,11 +1,6 @@
 # version format
 version: 1.0.{build}
 
-branches:
-  only:
-    - master
-    - feat/appveyor-artifacts
-
 environment:
   matrix:
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
@@ -14,6 +9,9 @@ environment:
 
 stack: python %PYTHON%
 
+cache:
+  - C:\Users\appveyor\.conan\data -> appveyor.yml
+
 install:
   - cmd: echo "Downloading conan..."
   - cmd: set PATH=%PYTHON%;%PYTHON%\Scripts;%PATH%