Support babel 7

[diegohaz]

Possibly checking the babel version in the project (cwd) and using babel-register or @babel/register depending on the version.

Relevant parts of the code:

singel/src/cli.js

Line 29 in 86d9fe6

require("babel-register")(finalBabelConfig);

singel/package.json

Line 46 in 86d9fe6

"babel-register": "^6.26.0",

[namjul]

@diegohaz do you want to keep support for babel 6?
Here an PR for babel 7 #28