Don't call slice on arguments

Don't use utils.forEach to loop over arguments

Update README.md: instantiation

Calling slice on arguments can prevent optimizations in some JS engines
(see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments).

This fixes IE8 support, where we cannot relialably detect an arguments
object.

Add support third-party library to serialize url params

Make axios instantiable

fixing http adapter WRT `responseType === 'arraybuffer'`

Don't include a process shim in the build

Update axios.d.ts, add Response.statusText

closes #116

closes #70, closes #98

Add grunt-cli and phantomjs dev deps

Added defaults.timeout to default config.

FIX typescript definition to correctly type promise callbacks

return result from callback

allow passing an agent through to node http requests, closes #68