Use path.join instead of path.resolve

This ensures the case of the path is consistent with how require resolves
paths.

Closes #2486

src/atom.coffee

@@ -151,8 +151,8 @@ class Atom extends Model
     {devMode, safeMode, resourcePath} = @getLoadSettings()
     configDirPath = @getConfigDirPath()
 
-    # Add 'src/exports' to module search path.
-    exportsPath = path.resolve(resourcePath, 'exports')
+    # Add 'exports' to module search path.
+    exportsPath = path.join(resourcePath, 'exports')
     require('module').globalPaths.push(exportsPath)
     # Still set NODE_PATH since tasks may need it.
     process.env.NODE_PATH = exportsPath