raw merge with clojure 1.5.1

hi karl,

i did merge clojure 1.5.1 in clj-ds. it is quite "raw".
i have change the snapshot version to 0.0.2-SNAPSHOT.

some remark:
- they added a new iterator for PersitentVector. I have named the method iterator151() and let your own version be the used version.
- I did not add the diverse new interfaces  like IHashEq to the TRIES classes that you have written.
- not a lot changed. some 'throws Exception' are away and some tuning was done in PersistentVector.

what do you think?

cheers!
stan.