1.9.4 Avoid an unexpected transpose

https://github.com/joey711/phyloseq/issues/320
https://github.com/joey711/phyloseq/pull/321

CHANGES IN VERSION 1.9.4
-------------------------

BUG FIXES

	- `rarefy_even_depth()` function no longer enforces an orientation.

	- It used to always coerce to OTU-by-sample orientation.

	- Solves Issue 320 https://github.com/joey711/phyloseq/issues/320
Merge branch 'audy-fix-rarefy_even_depth'