Merge pull request #5 from ksmolder/master

Added support for Lightning and address book
fix screenshot in README, moving bugs to issues
formatting
Fixes #7
Fixes #8
Removed transparancy overlay from event-color-boxes in today pane
Fixes #9
Avoid double border below calendar nav in multiweek and month view
Code cleanup and more use of native Elementary items
Added columnpicker icon
update textbox style (fixes #6)
box around message (like geary)
updated folder tree styling
Fixes #10
Use of elementary icons
Using size=menu instead of size=toolbarsmall results in sharper icon rendering
Implemeted new Granite-style sidebar selection
hack to make the title bar (looks better with no menu)
updated tabs background; darken splitters around message pane
removing geary style shadow, looks silly