ENH: update .gitignore, remove comments
ENH: update .gitignore, remove comments

On my system, .gitignore does not allow comments at the end of ignore
lines (it ignores the ignore line).

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