Add install help guide to contributing.md

- Users are prompted to view this guide before raising an issue. 
- Putting it here as well as in the wiki may help more people to see the info needed to debug their install.

CONTRIBUTING.md

@@ -2,6 +2,14 @@
 
 General guidelines for contributing to node-sqlite3
 
+## Install Help
+
+If you've landed here due to a failed install of `node-sqlite3` then feel free to create a [new issue](https://github.com/mapbox/node-sqlite3/issues/new) to ask for help. The most likely problem is that we do not yet provide pre-built binaries for your particular platform and so the `node-sqlite3` install attempted a source compile but failed because you are missing the [dependencies for node-gyp](https://github.com/TooTallNate/node-gyp#installation). But please provide as much detail on your problem as possible and we'll try to help. Please include:
+ - terminal logs of failed install (preferably from running `npm install sqlite3 --loglevel=info`)
+ - `node-sqlite3` version you tried to install
+ - node version you are running
+ - operating system and architecture you are running, e.g. `Windows 7 64 bit`.
+
 ## Developing / Pre-release
 
 Create a milestone for the next release on github. If all anticipated changes are back compatible then a `patch` release is in order. If minor API changes are needed then a `minor` release is in order. And a `major` bump is warranted if major API changes are needed.