fix: use babel-preset-es2015-ie to adapt ios8.x、Android4.x..

[HansJiang]

throung our monitoring,it doesn't work in ios8.x、Android4.x and the low version of web browser engines(eg:UC).

BABEL transforming ES6 classes to ES5 syntax has compatibility issues.

Links: same problem、 looseMode

It's a better way to use babel-preset-es2015-ie.

differences between babel-preset-es2015-ie and babel-preset-es2015

 [ [require('babel-plugin-transform-es2015-classes'), {loose: true}], require('babel-plugin-transform-proto-to-assign'), ] 

[broven]

@SanichKotikov same problem I met, this PR look good to me

[SanichKotikov]

@broven @HansJiang maybe it's better to use this #243 ?