Added contributing information

CONTRIBUTING.md

@@ -1,4 +1,35 @@
-## Code formatting
+# Contributing to Cutter
+
+There are many ways you can contribute to cutter.
+The easy one is to open issues with bugs you found on the application.
+The second one is to fix issues found in the GitHub issues tracker.
+
+## Opening an issue
+
+Make a clear description of the bug/feature, use screenshots, send binaries, etc.
+
+## Contributing to the code
+
+Note that cutter is still under development and many parts of the code are to be improved.
+
+### Calling a radare2 command
+
+There are two ways to do it:
+* `CutterCore::cmd()` *(Discouraged)* Only use it for commands which yells no output
+* `CutterCore::cmdj()` To be used with json commands like `cmdj("agj")` or `cmdj("aflj")`. It is way easier to parse a json output.
+
+### Seek the current file
+
+To modify radare2 seek use `MainWindow::seek(const RVA offset)`. This is important because it will emit a `MainWindow::seekChanged(RVA offset)` signal.
+Never ever call cmd("s offset");
+
+### Creating a widget
+
+Make sure to connect the `MainWindow::seekChanged(RVA offset)` signal so your widget refreshes its output when radare2 seek is modified (switching to another function, etc.).
+
+## General coding guidelines
+
+### Code formatting
 
 We use [AStyle 2.06](https://sourceforge.net/projects/astyle/files/astyle/astyle%202.06/) to format the code. The command line for formatting the code according to the style is: