"ELMo's Friends" paper experiment code

s2s decoder update (make more params active; add projection layer) (#…

…384)

* quick fix for mt

* [veryminor] add mt_attention parameter to defaults.conf

* readme: mt->s2s

* [s2sdecoder] add bottleneck layer

* [s2sdecoder] make all parameters active

* clean beamsearch

* pull/384: address comments

* fix merge

* Add s2s_ prefix to opts; add projection documentation in code

* Rename s2s configs + refactor param dict construction; fix scheduled sampling bug; fix projected dim bug

* Redo decoder param construction

* Remove unneeded code

* Remove hasattr calls; fix bug when no attn

* Fix wrong param name