Plotting: imperfect alignment of color and coordinate grids

[ikamensh]

For some reason the colored cells are slightly (and visibly) misaligned with the coordinate grid.

Reproducible with:

import numpy as np
from matplotlib import pyplot as plt
from arc.plot import plot_grid


grid = np.zeros([4,4], dtype=np.uint8)

for i in range(4):
    grid[i,i] = 3

plot_grid(grid)
plt.show()