Update collections which moved out of tree

As we all know: [Gankro keeps stealing collections.](http://www.reddit.com/r/rust/comments/2pme5d/collectrs_enbiggens_treemap_triemap_enumset/)
The following changes are required given the collections present in `rustc 0.13.0-nightly (cc19e3380 2014-12-20 20:00:36 +0000)`

This patch provides implementations for :
* `TreeMap` -> `BTreeMap`
* `TreeSet` -> `BTreeSet`

This removes the implementations for 
* `TrieMap` -> `()`
* `TrieSet` -> `()`