Merge branch 'release/v0.3.0' into develop
Add new screenshot for version 0.3.0 and remove old ones
Add link to homepage to about dialog
Start of find & replace function

Add widget beneath text editor that shows the
find & replace UI.
Add several new css styles
New style and theme

Add Clearness and Clearness Dark as new css style and highlighting theme.
Add 16x16 icon for close buttons
Improve find/replace function

It's now possible to find forward and backward in the
markdown text.
Add several new icons to icon engine
Add icon to find/replace action
Implement replace & replace all functions

The replace and replace all buttons in the find/replace widget are working
now.
Better scrollbar handling after update

stay at current scrollbar position when live preview is updated
Merge branch 'feature/find-replace' into develop

Closes issue #21
Remove unused action
Document statistics

Show word count of markdown document to statusbar.
Improved word count
Document statistics

Add line, word and character count to tooltip of word count label.
Improve export to PDF

Add specific dialog to the export to PDF function. The user can now choose
the paper size and orientation.

Closes issue #19
add config for travis-ci.org
fix config for travis-ci.org