Removed the "VERSION" file, as it breaks JRuby compiled JARs

I'm curious as to why this pattern is/was used.

```
Errno::ENOENT: No such file or directory - file:/usr/lib/...jar!/gems/mail-2.5.4/lib/mail/../VERSION
     read at org/jruby/RubyIO.java:3776
     read at org/jruby/RubyIO.java:3955
```
Please don't change the interface here.