fix rendering of dropdown lists
(broke in 030103997c3721bb378ee280a8af8cc42060b9b4)
remove bottom margin for <select> elements too (fixes #69)
fix broken logic in TbHtml::addCssClass()

The pattern used in preg_match() doesn't work as intended since e.g. a
dash is treated as a word boundary. With this change the class string
is always operated on as an array and also removes the possibility of
accidentally ending up with duplicate class names.
fixed logic error which broke the build
Merge pull request #100 from Jalle19/fix-select-size

Fix rendering of dropdown lists since 030103997c3721bb378ee280a8af8cc42060b9b4
Merge pull request #103 from Jalle19/refactor-addcssclass

Fix broken logic in TbHtml::addCssClass()
Merge pull request #102 from Jalle19/fix-select-filter

Remove bottom margin for <select> elements too (fixes #69)