Add label to statusbar that shows the current CSS style for the HTML preview
Show UI as fast as possible

Use QTimer::singleShot() for initialization to show UI as fast as
possible.
Add html source view

closes issue #6

- add QPlainTextEdit that shows the generated HTML source.
- add a subclass of QLabel that sends a signal when double clicked.
- use new ActiveLabel class in statusbar to switch between HTML preview
  and source.
Add peg-markdown-highlight library

Add subproject for peg-markdown-highlight library with qmake project for building it
as static library.
Add link reference to new peg-markdown-highlight library
Fix compile/link for MINGW
First version of highlighting in markdown editor

Add new classes MarkdownHighlighter and HighlightWorkerThread to support
syntax highlighting in the markdown editor.

issue #3
Remove debug statements and nicely end worker thread
Move parsing of syntax highlighting styles

Move parsing of syntax highlighting styles to own new class StyleParser.
This new class also supports retrieving a color palette for the text
editor from the style.

issue #3
Add about dialog

Add a menu entry and a simple about dialog

closes issue #7
Improved theme support

* Organize themes and styles in subfolders
* Automatic change of syntax highlighting theme when
  corresponding css style changes
* replace clearness and clearness-dark with solarized-light
  and solarized-dark

issue #3
Merge branch 'feature-markdown-highlight' into develop

closes issue #3
First version of export support to PDF and HTML
small changes in syntax highlighting functionality
Add HTML templates

Use template files to surround generated HTML.
Correct markdown syntax highlighting

Fix check for empty results from syntax highlighting
Add file for licenses
Merge branch 'develop'