Create CONTRIBUTING.md (#136)

Includes most of the common errors that cause eslint to fail.

Added syntax highlighting

Added sample eslint pre-commit hook

CONTRIBUTING.md

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+Gnome.org requires that extensions have roughly the same styles.  
+
+Here are a few important ones and their explanations.<br>
+**NOTE: This doc is best viewed in markdown and not as plaintext**
+1.  Statements must end a semicolon (even if it runs properly without it)
+1.  Lines must not have any extra space at the end (including blank lines)
+1.  Use 4 spaces instead of tabs
+3.  Switch statements and their cases must be at the same indent level
+    ```javascript
+    // good
+    switch (direction) {
+    case 'left':
+        doStuff();
+    }
+
+    // bad
+    switch (direction) {
+        case 'left':
+            doStuff();
+    }
+
+    ```
+1.  If statements and their curly braces must have a space between them
+1.  If statements and their else block that only have a single command must not be surrounded with curly braces.
+    ```javascript
+    // good
+    if ( user.age > 21 )
+        user.canDrink = true;
+    
+    // bad
+    if ( user.age > 18 ) {
+        user.canSmoke = true;
+    }
+    ```
+1.  Multi-line objects must have a trailing comma as if there was another element
+    ```javascript
+    var goodObject = {
+        firstElement: 1, // <--- trailing comma
+    };
+    
+    var badObject = {
+        onlyElement: 1
+    }
+    ```
+1.  Use camelCase names instead of snake_case_names
+    ```javascript
+    var goodName; // good
+    var bad_name; // bad
+    ```
+1.  Strings MUST be single quoted
+    ```javascript
+    var blah = 'I\'m a single quoted string'; // good
+    var blah = "I'm a double quoted string"; // bad 
+    ```
+1.  Use backtick interpolation instead of concatenation
+    ```javascript
+    var builtString = `Hello, ${useName}!`; // good
+    var concatString = 'Hello, ' + userName + '!'; // bad
+    ```
+1.  Functions must have jsdoc strings that give the variable name, type, and explanation for EACH variable
+    ```javascript
+    // good example
+    /**
+     *
+     * @param {object} app - the window object
+     * @param {number} x - desired x value
+     * @param {number} y - desired y value
+     * @param {number} w - desired width
+     * @param {number} h - desired height
+     */
+    function moveAppCoordinates(app, x, y, w, h) {
+    .....
+
+    ```
+1.  Comparisons must use 3 signs instead of 2. ( === and !== instead of == and != )
+    ```javascript
+    // good
+    log( firstName === 'Weadababy' );
+    
+    // bad
+    log( lastName == 'Eetzaboi' );
+
+It's highly suggested that you lint your code with the .eslintrc.yml we included in the base of the repo with the `--fix` option before submitting Pull requests.
+Pull requests that fail the lint test will not be accepted and must be fixed before consideration.
+
+I also suggest adding this .git/hooks/pre-commit to your copy of the repo.
+```bash
+#!/bin/bash
+cd "$(git rev-parse --show-toplevel)"
+ESLINT="node_modules/.bin/eslint"
+pwd
+
+if [[ ! -x "$ESLINT" ]]; then
+  printf "\t\033[41mPlease install ESlint\033[0m (npm install eslint)\n"
+  exit 1
+fi
+
+STAGED_FILES=($(git diff --cached --name-only --diff-filter=ACM | grep ".jsx\{0,1\}$"))
+
+echo "ESLint'ing ${#STAGED_FILES[@]} files"
+
+if [[ "$STAGED_FILES" = "" ]]; then
+  exit 0
+fi
+
+$ESLINT "${STAGED_FILES[@]}" --fix
+
+ESLINT_EXIT="$?"
+
+# Re-add files since they may have been fixed
+git add "${STAGED_FILES[@]}"
+
+if [[ "${ESLINT_EXIT}" == 0 ]]; then
+  printf "\n\033[42mCOMMIT SUCCEEDED\033[0m\n"
+else
+  printf "\n\033[41mCOMMIT FAILED:\033[0m Fix eslint errors and try again\n"
+  exit 1
+fi
+
+exit $?
+```