'Add to homescreen' feature on ipad with icon

add meta to support  ipad.  When add to home screen ,Stackedit can run
in standalone mode ,and can be an offline app even without connections.
update logo
Fixed google authorization popup. Fixes #495
Fixed viewer issues
Fixed focus on show modal
Fixed preview button drag on touch screen
Replace grunt by gulp
Prepare release
Prepare release
Upgrade to mathjax 2.4
Fixed wkhtmltopdf parameters. Fixes #501
Prepare release
Version 4.1.4
Prepare release
Fixed end of line issue on IE
Fixed viewport issue with pageup/pagedown on chrome. Fixes #505
Fixed title editing issue on IE
Prepare release
Added Gulp to pre-requisites
Added Solarized light and dark theme.

- Themes share the common solarized.less base.
n branch master