leaflet.extras2 1.2.0

• Included Arrowheads plugin
• Included Leaflet.Sync plugin
• Included Leaflet MovingMarkers plugin
• Included Leaflet Spin plugin. Thanks to @radbasa
• Included Labelgun plugin.
• addTimeslider gained styling options and the arguments label, labelOptions, sameDate and ordertime and works for Point / Linestring Simple Feature Collections
• Enable multiple sidebars. Thanks to @jeffreyhanson
• Option fit removed for sidebars as plugin CSS/JS was adapted
• Deprecated menuItem/mapmenuItems/markermenuItems and renamed with prefix context_. Fixes #10 and #17
• Some improvement for the easyprint plugin: (Fixes #31)
  • It is now possible to include multiple custom sizeModes in easyprintOptions. The example easyprint_app.R has been extended to demonstrate the new functionalities.
  • The tileLayer option now accepts a group name for a tilelayer for which printing will wait until the layer is fully loaded.
• The addPlayback is now capable of displaying labels and popups for every timestep. The transition of labels and popups can be controlled with transitionpopup and transitionlabel.
• The function addHistory now requires the fontawesome package, since the dependency is not included in shiny's shared directory anymore.
• The function addWMS gained the argument checkempty, which will check the returning HTML-body tag. If the body is empty, no popup is opened.
• The function addMovingMarker now accepts icons created by makeAwesomeIcon.