TST: please skip tests needing up-to-date xlrd
```
======================================================================
ERROR: test_excel_010_hemstring (pandas.io.tests.test_excel.ExcelTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/yoh/deb/gits/pkg-exppsy/pandas/debian/tmp/usr/lib/python2.7/dist-packages/pandas/io/tests/test_excel.py", line 836, in test_excel_010_hemstring
    res = roundtrip(df)
  File "/home/yoh/deb/gits/pkg-exppsy/pandas/debian/tmp/usr/lib/python2.7/dist-packages/pandas/io/tests/test_excel.py", line 826, in roundtrip
    xf = pd.ExcelFile(path)
  File "/home/yoh/deb/gits/pkg-exppsy/pandas/debian/tmp/usr/lib/python2.7/dist-packages/pandas/io/excel.py", line 65, in __init__
    raise ImportError("pandas requires xlrd >= 0.9.0 for excel support, current version "+xlrd.__VERSION__)
ImportError: pandas requires xlrd >= 0.9.0 for excel support, current version 0.6.1


======================================================================
ERROR: test_to_excel (pandas.tests.test_panel.TestPanel)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/yoh/deb/gits/pkg-exppsy/pandas/debian/tmp/usr/lib/python2.7/dist-packages/pandas/tests/test_panel.py", line 1378, in test_to_excel
    reader = ExcelFile(path)
  File "/home/yoh/deb/gits/pkg-exppsy/pandas/debian/tmp/usr/lib/python2.7/dist-packages/pandas/io/excel.py", line 65, in __init__
    raise ImportError("pandas requires xlrd >= 0.9.0 for excel support, current version "+xlrd.__VERSION__)
ImportError: pandas requires xlrd >= 0.9.0 for excel support, current version 0.6.1
```
