Minor changes in the contribution guidelines and added to README #39

Author: SSBMTonberry

CONTRIBUTION.md

@@ -1,4 +1,4 @@
-## Contribution guidelines
+# Contribution guidelines
 
 It's great that people want to contribute to Tileson!
 Here are some guidelines to make sure we keep this a stable library.
@@ -8,6 +8,11 @@ In short this means that I must be aware of an issue and accept it before it can
 Reason being mainly to make sure the issue actually is a problem and that I retain full control of project and its direction. 
 If the issue is about a potential new feature, it's important that you describe in detail why this feature is needed.
 
+Also: If you are interested in fixing or developing on an existing issue you did not
+create yourself, please notify me in the issue before you start working on it, so I 
+can assign you the task. This is mainly to prevent that two people work on the 
+same feature.
+
 ### 2. Every issue must have a unit test proving that it works
 If you have either fixed a bug or created a new feature, you must prove that everything works
 as intended by creating a test to prove that the logic works. Additionally, 

README.md

@@ -11,12 +11,16 @@ maps made with newer versions of Tiled just as well.
 
 Be sure to take a look at the release notes to see what's new!
 
-## Documentation
+# Documentation
 
 There is a `Doxygen` generated documentation of Tileson that can be found [HERE](https://ssbmtonberry.github.io/tileson/html)
 
 ### IMPORTANT: Tileson requires that everything it needs in a map is embedded into it, to be able to resolve their related objects. Maps having external references to tilesets etc. will not work.
 
+# How to contribute
+You are free to post any issue requesting new features, reporting bugs or asking questions at any time.
+If you want to contribute in the development of `Tileson`, make sure you read the [CONTRIBUTION GUIDELINES](https://github.com/SSBMTonberry/tileson/blob/master/CONTRIBUTION.md)
+before you start doing anything.
 
 # Tileson is header-only!
 This means that all you need is one file, `single_include/tileson.hpp` to have Tileson going