MAINT more fixes

* problem installing data_files in libqstrung (I didn't manage), workaround install it other stats.tests folder PR #898 wasn't correct and none of the versions I tried worked, I opened issue #907 for a proper solution
* lower precision in a lowess test that fails sometimes #897
* fix a test in iolib. test_table with indeterministic squence with older pandas see #831
* add inter_rater to docs #733 


#831 listed some py 2.6 older pandas errors and failures, they are all fixed now

test suite runs without errors or failures on python 2.6 numpy 1.5.1 pandas 0.7.3 scipy 0.9.0
and on python 3.3 with the newest released versions of numpy, pandas, scipy

some tests are disabled with older versions of pandas