add mod.deps to ref it's depenceses #1255

to avoid config bug before exe
update sea require
fix unend comment
use hash instead of array to improve performance
#https://github.com/spmjs/spm/issues/884
fix config charset with a function
Update index.html
use mod.exports when 'exec' emit
fixed #1265, return module.exports
Merge pull request #1266 from hotoo/fix-1265

fixed #1265, return module.exports
Delete unused var .
Merge pull request #1268 from hotoo/fix-rm-fn

Delete unused var `fn`.
Update CONTRIBUTING.md

Fix the dead link for 'How To Ask Questions The Smart Way'
Merge pull request #1270 from lord63/master

Fix the dead link for 'How To Ask Questions The Smart Way'
realpath for ever uri #1271
Add isBrowser and isWebWorker variables
Wrap browser specific code in if-else block
Implement web worker support.

1. Get `loaderDir` from `Error.stack`
2. Use `importScripts` to load script
Fix name collision
Add test for web worker