Update and rename README.rdoc to README.md (#3)

* Update and rename README.rdoc to README.md

Fixes #1

Author: dkastl

README.md

@@ -0,0 +1,74 @@
+# Redmine Geo-Task-Tracker (GTT) Plugin
+
+The Geo-Task-Tracker (GTT) plugin adds spatial capabilities to Redmine:
+
+- Locate your issues as point, line or polygon
+- Show and filter issues on a map
+- Specify a project area
+- Store the location of a user
+- Extends Redmine API
+- Geocoding
+- and more
+
+## Project health
+
+[TBD]
+
+## Requirements
+
+Redmine GTT plugins **require PostgreSQL/PostGIS** and will not work with SQLite or MariaDB/MySQL!!!
+
+- Redmine >= 3.4.0
+- PostgreSQL >= 9.6
+- PostGIS >= 2.4
+
+## Installation
+
+Create a PostGIS-enabled database:
+
+```
+createdb -U postgres -O redmine redmine
+psql -U postgres -d redmine -c "CREATE EXTENSION postgis;"
+```
+
+To install Redmine GTT plugin, download or clone this repository in your Redmine installation plugins directory!
+
+```
+cd path/to/plugin/directory
+git clone https://github.com/gtt-project/redmine_gtt.git
+```
+
+Then run
+
+```
+bundle install
+bundle exec rake redmine:plugins:migrate
+```
+
+After restarting Redmine, you should be able to see the Redmine GTT plugin in the Plugins page.
+
+More information on installing (and uninstalling) Redmine plugins can be found here: http://www.redmine.org/wiki/redmine/Plugins
+
+## How to use
+
+[Settings, screenshots, etc.]
+
+## Contributing and Support
+
+The GTT Project appreciates any [contributions](https://github.com/gtt-project/.github/blob/main/CONTRIBUTING.md)! Feel free to contact us for [reporting problems and support](https://github.com/gtt-project/.github/blob/main/CONTRIBUTING.md).
+
+## Version History
+
+[TBD]
+
+## Authors
+
+  - [Jens Kraemer](https://github.com/jkraemer)
+  - [Daniel Kastl](https://github.com/dkastl)
+  - [Thibault Mutabazi](https://github.com/eyewritecode)
+  - [Ko Nagase](https://github.com/sanak)
+  - ... [and others](https://github.com/gtt-project/redmine_gtt/graphs/contributors)
+
+## LICENSE
+
+This program is free software. See [LICENSE](LICENSE) for more information.