Has-played attribute and fixes

• Move test related in one test folder (#167) 75ff9b6
• fix: seek back button always used default value for aria label (#164) d053fe9
• fix/loading-indicator-svg-aria-hidden: aria-hide svg like we do other svgs (aria responsibilities belong to the elements). (#163) 83c3994
• fix/configurable-seek-aria-labels: Update aria labels appropriately when seek forward/backward button offsets change. (#162) 37a6214
• add has-played attribute (#160) 8a41912

v0.5.0...v0.5.1