Fixing ie8 error

[jinzhubaofu]

there are errors on ie8 when using the minified version.

the source code here

var axios = module.exports = function axios(config) {
   // operations with axios
}

will be minifed into

var a = module.exports = function b(config) {
  // operations with b
  // but a !== b and b.interceptors undefined on ie8
};

but on ie8, in the function b, a !== b, b has no attributes like interceptors, so it will crash.

I write a demo, you can check it out here

just remove function name axios will be ok.

[mzabriskie]

Thanks for the PR. Can you remove the dist/ folder. This should only be updated when releasing. Also, I think I would prefer module.exports = function axios, as opposed to using an anonymous function.