DOC(BF): fix assumption about chunks indexes in tutorial_classifiers

before we started numbering of chunks from 0.
In openfmri layout of the tutorial we start with 1 (e.g. run001)
that is why odd/even runs notion flips (we start with odd 1 now, not even 0 as before).
ENH: use getcwd() (full path) instead of curdir (just .) for pymvpa_datadbroot
Merge pull request #263 from yarikoptic/master

BF+ENH:  fixing tutorial_classifiers for openfmri layout chunk indexing + let's use full path to datadb