added string builder extension methods. Added a few more tests to get 100% code coverage.
Renamed "PrependLine" to "AppendLineBefore" as the method appends a newline before the value provided, instead of prepending a line to the current content of the string builder (as the name might suggest).
css-like box model styling. still working on tests.
100% code coverage achieved with bug fix.
Added PickyReplace method (not implemented) and some tests.
More tests needed, and tests should be reworked to use autofixture if possible.