Read / write support for Conditional Formatting.
Conditional Formatting fix.
Updated comment.
Conditional Formatting fixes.
Conditional Formatting fixes.
Conditional Formatting tests.
Added cell-is conditional formatting.
Added style documentation.

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rename : doc/source/tutorial.rst => doc/source/styles.rst
Merged conditional formatting.

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branch : 1.8
Removed QName when reading conditional formatting.

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branch : 1.8
Removed QName from styles.

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branch : 1.8
Updated tests for conditional formatting.

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branch : 1.8
Verify structure when writing dxfs.

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branch : 1.8
Prevent default column definition from creating large amounts of columns when writing.

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branch : 1.8
Updated column style in test.

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branch : 1.8
Merged in current 1.8 branch

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branch : 1.8
Updated column style in test.

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branch : 1.8
Merged ericgazoni/openpyxl/1.8 into 1.8

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branch : 1.8
Moved conditional formatting if/elif to dict mapping.

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branch : 1.8
Merged ericgazoni/openpyxl/1.8 into 1.8

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branch : 1.8