Added missing \t to #617 unit test, that was also treated wrong
moved utility method to test case superclass
added unit test for #434
added demo for letter-spacing #434
modified kerning method name
added kerning tests to writer #434
Added -kerning to attributes dictionary methods #434
added synchronized to text block method
Implemented reader and writer support for letter-spacing #434
removed old stuff
Merge branch 'od/issue_434' into develop