Add Travis build status

and minor reformatting
Added a few authors to AUTHORS.rst
DOC: remove $ from shell commands

they are obscure for non expert users and tend to be copied and pasted
verbatim, fixes #312
Updated nilearn description in README.rst

Used the wording from the website home page
Update list of authors in doc/AUTHORS.rst
Change expected mask name in fetch_localizer_contrasts

fixes #295
replaced outdated comments by check_niimgs
Merge pull request #321 from banilo/comments

remove obsolete comments
Promote data folder into packages

to remove warnings when installing with pip. Tweak setup.py accordingly
Use filename variables in examples

to make it more obvious that the _img functions can take filenames as input. Other minor fixes
went in while I was at it.