Create feature-idea.md

Resolves #14.

Author: nathanjmcdougall

.github/ISSUE_TEMPLATE/feature-idea.md

@@ -0,0 +1,14 @@
+---
+name: Feature Idea
+about: A high-level description of a feature you'd like.
+title: ''
+labels: ''
+assignees: nathanjmcdougall
+
+---
+
+**Motivation**
+A clear and concise description of what benefit you would get from this feature.
+
+**Summary of desired feature**
+A clear and concise description of what you want to happen, at a high level.