Use S3 bucket to mirror unreliable IronPython and Jython installers

Use S3 bucket to mirror unreliable IronPython and Jython installers

For now I have left the mirror of IronPython and Jython as public URLs on my bucket. I don't see any need to change that for now.

I hope this works for you, if not I will look at it more tomorrow. 

PS You may want to turn off the (much more complicated) test build until you get the main build running, especially as it will shorten your turnaround time as you fiddle with secure variables and the like. I think this diff should do it:

```
diff --git a/.travis.yml b/.travis.yml
index cf44833..9ad06a0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,7 +13,6 @@ language: java
 
 env:
   matrix:
-    - PYDEV_TEST=true
     - PYDEV_TEST=false
   global:
     # Set the DISPLAY to match the one started with xvfb below
```

Jonah