Make the graphie encompass the axis labels

Summary: The graphie wasn't large enough to encompass the labels, so the
`y` label was intersecting the input box. This fixes that. (I think this
is recent, as a result of moving the answer box around)

Test plan:
 - Load http://exercises.ka.local/exercises/graphing_points.html?problem=give-coord-both
 - Load http://exercises.ka.local/exercises/graphing_points.html?problem=give-coord
   - Ensure the `y` label doesn't intersect the input box in both

Auditors: alex, eater