Project files, .gitignore, Linux installer, Markdown

I added installer, which allows you to run SubtitleNET as standard executable. Example:
```
user@pc:$ subtitlenet PATH_TO_MOVIE
```

Then I removed project files from repository, also added them to `.gitignore` (which was added too).

Last change was rename of `readme.txt` to `readme.md`, which added Markdown support.