v2.1.0 (Swift 3.0)

• Fix #30: add keyboard return key type (ty @ShiWeiCN)
• Fix #29: switching readonly on and off (ty @treyrich)
• Fix #25: add inputFieldAccessoryView property
• Fix #24: add onDidSelectTagView and onDidUnselectTagView event
• Enhancement: add selectNextTag and selectPrevTag methods