Add issue template

[manidlou]

Added issue template. I am not sure about the wording though! Please change it any way that you think is appropriate! 😄

[coveralls]

Coverage remained the same at 87.377% when pulling 32c821d on issue-template into 2599b67 on master.

[RyanZim]

How about this:

<!-- Please fill out the following information if it applies to your issue: -->
- **Operating System:**
- **Node.js version:**
- **`fs-extra` version:**

In my experience; the people that tend to file issues without the needed info, and therefore need an issue template, tend to leave the template text almost untouched. Therefore, I recommend putting the instructions in an HTML comment.

[coveralls]

Coverage remained the same at 87.377% when pulling b77ee63 on issue-template into 2599b67 on master.