Add spm support

[afc163]

A nicer package manager: http://spmjs.io
Documentation: http://spmjs.io/documentation

http://spmjs.io/package/vue

---

It is a package manager based on Sea.js which is a popular module loader in China.

spmjs focus in browser side. We supply a complete lifecycle managment of package by using spm.

If you need ownership of vue in spmjs, I can add it for your account after signing in http://spmjs.io.

[yyx990803]

Hmm, I'd like to support spm, but a few issues (as have been raised by other package authors):

1. Could .spmignore be just an ignore field under the spm namespace in package.json? I don't really want to add an extra dot file. It seems this has been a pretty big issue for package authors to adopt spm.
2. I only show badges that are related to the build/test status, so no package badges please.

[afc163]

Now we support ignore field in package.json, and remove badge in this PR.

[yyx990803]

Could you please follow the ignore patterns in the project's bower.json (plus dist)?

[afc163]

package.json is useful for spm install so we don't ignore it. Except that, the ignore is the same as bower.json now.

[yyx990803]

Looks good to merge. One final thing: can you point the PR to the dev branch instead? You might need to close this one and open a new PR.

[afc163]

https://github.com/yyx990803/vue/pull/326