right-associative implicit call

[As discussed on the mailing list](https://groups.google.com/d/topic/metascript/Nf0PBBht_zs) here are some changes to make the *space operator* have less precedence than member access and be right associative.

    a b        ; a(b)
    a b c      ; a(b(c))
    a b.c      ; a(b.c)
    a.b c.d    ; a.b(c.d)
    a(b c)(d) ; a(b(c))(d)

I certainly prefer this syntax, the right associativity works like in coffeescript and seems to work quite well to interact with Javascript code, which doesn't apply currying normally. Although if you prefer to keep it with left associativity I could certainly live with that if it still respects member precedence.