Misleading tiles() iterator

[sbquinlan]

The tiles() iterator for 'WebMercatorQuad' can return incorrect tile coordinates. The 'truncate' option in this case is misleading. The truncate_lnglat method it uses in utils.py is hard coded to bound coordinates to [-180, 180] and [-90, 90] irrespective of the TMS's bounds (in this case, correctly described in the warning).

I believe a less misleading interface would be to bound the coordinates by self.bbox in tiles().

Expected Result:

>>> import morecantile
>>> tms = morecantile.tms.get('WebMercatorQuad')
>>> tiles = list(tms.tiles(-180., -90., 180., 90., range(1), truncate=True))
<redacted>/.venv/lib/python3.8/site-packages/morecantile/models.py:450: PointOutsideTMSBounds: Point (-179.99999999999, 89.99999999999) is outside TMS bounds [-179.9999999999996, -85.05112877980656, 179.9999999999996, 85.05112877980656].
  warnings.warn(
<redacted>/.venv/lib/python3.8/site-packages/morecantile/models.py:450: PointOutsideTMSBounds: Point (179.99999999999, -89.99999999999) is outside TMS bounds [-179.9999999999996, -85.05112877980656, 179.9999999999996, 85.05112877980656].
  warnings.warn(
>>> tiles
[Tile(x=0, y=0, z=0)]

Actual Result:

>>> import morecantile
>>> tms = morecantile.tms.get('WebMercatorQuad')
>>> tiles = list(tms.tiles(-180., -90., 180., 90., range(1), truncate=True))
<redacted>/.venv/lib/python3.8/site-packages/morecantile/models.py:450: PointOutsideTMSBounds: Point (-179.99999999999, 89.99999999999) is outside TMS bounds [-179.9999999999996, -85.05112877980656, 179.9999999999996, 85.05112877980656].
  warnings.warn(
<redacted>/.venv/lib/python3.8/site-packages/morecantile/models.py:450: PointOutsideTMSBounds: Point (179.99999999999, -89.99999999999) is outside TMS bounds [-179.9999999999996, -85.05112877980656, 179.9999999999996, 85.05112877980656].
  warnings.warn(
>>> tiles
[Tile(x=0, y=0, z=0), Tile(x=0, y=1, z=0)]