Upgrade to Clojure 1.6
Support multiple back-to-back empty statements
Change some space into non line-ending space

For example, the code `a.b += 1` should not be parsable from

```
a.b
+= 1
```

Also renamed the rule to better indicate its meaning, and added a new
rule to allow `when` to continue working with preceding empty lines.
Move alternation operators to the next line