Improve browser support with tests and slim dependencies

[jbmusso]

Browser support should be improved:

• add appropriate tests
• remove dependencies/unsure the slimmest possible bundle

[dmill-bz]

FYI iOS browsers run in strict mode and throw the following error:

Const declarations are not supported in strict mode.

[jbmusso]

This is weird. The code published to npm (and its dependencies) is transpiled to ES5 and shouldn't have any const declarations (only var). Could you be more specific as to how you import the client to your application?

[dmill-bz]

I originally thought it was because of some of your dependencies (and you excluding node_modules from webpack). But looking at the code again it seems to remove all const appropriately. Wonder why the behavior on gremlin-bin is different. I'll give this another look.