Added test for #222. Needs more investigation as to where the problem is exactly.

--HG--
branch : 1.8
Make test fail.

--HG--
branch : 1.8
Add a configuration for tests which are expected to fail.

--HG--
branch : 1.8
Added docstrings to global fixtures.

--HG--
branch : 1.8
Enable type inference for References - it’s lazy and will only be calculated when the values are called.

--HG--
branch : 1.8
Improve data_type inference checking.

--HG--
branch : 1.8
Whitespace

--HG--
branch : 1.8
Ensure a data type is set for labels.

--HG--
branch : 1.8
Unit test for non-numeric series such as axes or labels.

--HG--
branch : 1.8
Restrict Series and References to cells with values. Updated sample file which no longer causes problems in Windows.

--HG--
branch : 1.8