Add contribution guidelines, issue template and PR template

Author: langerhans

.github/CONTRIBUTING.md

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+# Contributing
+Thank you for wanting to help with this project! Pull requests and bug reports are always welcome, there are just some small things you should review before submitting.
+
+## Issues
+If you find any issue with the library, feel free to open an issue report. If it's just a small issue you might want to consider just asking on Slack (see below).
+
+## Feature Requests
+You may open an issue also to request new features. Make sure you describe what you are missing in the library and add any pointers someone might need to implement it.
+
+## Pull Requests
+If you consider submitting a pull request, please note the following:
+
+1. All pull requests **must** be submitted to the `Development` branch. The `master` branch is exclusively mutable by release. PRs against `master` will not be merged.
+2. Pleae make sure you follow the projects code style. To make sure you did, you can use `./gradlew checkstyleMain`.
+3. The project is licensed under [GNU GPLv3](../LICENSE.txt) thus all code you submit will be subject to this license.
+
+## Contact
+If you have any questions regarding the library you can ask those on the `#javaapi` channel on the [Pokemon GO Reverse Engineering Slack](https://pkre.slack.com/). You can [get your invite here](https://shielded-earth-81203.herokuapp.com/).

.github/ISSUE_TEMPLATE.md

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+**Description:**
+[Short description of the issue observed. If this ia feature request you can modify the template as required.]
+
+**Steps to reproduce:**
+
+1. [Step 1]
+2. [Step 2]
+
+**Expected behavior:**
+[What should happen?]
+
+**Actual behavior:**
+[What actually happens]
+
+**Stacktrace (If it's a crash):**
+[Please use pastebin if it's too long]
+
+**Version:**
+[The version of the lib you used]

.github/PULL_REQUEST_TEMPLATE.md

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+### Prerequisites (Remove this section if you want)
+Make sure you...
+
+* Follow the [contribution guidelines](CONTRIBUTING.md)
+* Follow the code style (run `./gradlew checkstyleMain`)
+* Submit this PR against the `Development` branch.
+
+**Fixed issue:** [Reference the issue number here, or remove if not a fix]
+
+**Changes made:**
+
+* List your changes here
+* Change 2...