add resolve_all to page rotation attr

[austinzy]

rotation.pdf

p = Page(self, page, page_number=page_number, initial_doctop=doctop)
  File "venv/lib/python3.7/site-packages/pdfplumber/page.py", line 22, in __init__
    _rotation = self.decimalize(self.page_obj.attrs.get("Rotate", 0))
  File "venv/lib/python3.7/site-packages/pdfplumber/page.py", line 50, in decimalize
    return utils.decimalize(x, self.pdf.precision)
  File "venv/lib/python3.7/site-packages/pdfplumber/utils.py", line 117, in decimalize
    return _decimalize(v, q)
  File "venv/lib/python3.7/site-packages/pdfplumber/utils.py", line 110, in _decimalize
    raise ValueError("Cannot convert {0} to Decimal.".format(v))
ValueError: Cannot convert <PDFObjRef:8> to Decimal.

[jsvine]

Thank you, @austinzy. Looks like a good catch. I'll aim to take a closer look soon, with the goal of merging.

[jsvine]

Merged and now available in v0.5.13. Thanks again.