BF - fix doctest floating point display error
BF - fix doctest floating point display error

On OSX 10.5 we get 1.499... instead of 1.5 for the repr; use str
instead.

alexis-roche/nireg,alexis-roche/nipy,alexis-roche/nipy,nipy/nipy-labs,arokem/nipy,nipy/nireg,alexis-roche/nireg,alexis-roche/register,arokem/nipy,nipy/nipy-labs,alexis-roche/register,bthirion/nipy,alexis-roche/niseg,bthirion/nipy,bthirion/nipy,arokem/nipy,alexis-roche/niseg,alexis-roche/nipy,bthirion/nipy,alexis-roche/register,alexis-roche/nipy,nipy/nireg,arokem/nipy