Remove Overview heading from README
Add define_column stubs
Write define_column unit tests
Remove length param from define_column
Redo internal states and move column test cases around
define_column passes unit tests, but doesn't do anything
Allocate column and add to columns list
Free columns
Allocate name and fmt with column structure
Add test case for out-of-order free
Add nomem test case for define_column
Add end_columns stub
Complete end_columns test cases
Fix memory leaks in test cases
Merge branch implementing columns functions and test cases