Only minor syntactic sugar removed from ES6 to ES5

[elingerojo]

Fixes #65

Approach

1. One step, one commit. For easy review.
2. Start by setting the wanted Node support to work toward getting the Travis CI green arrow.
3. Only remove syntactic sugar to be ES5 compatible
4. Squash commits at merge if desired

[zeke]

It looks like class OnigRegExp was already commented out. What about just removing that code instead of converting it to ES5?

[elingerojo]

I did the comment out after converting to ES5 and left the comments for easy review.
The change is needed to get back Node 4 support

• Updated with a new commit with comments removed just now

[zeke]

Looks good to me. What do you think, @maxbrunsfeld?

[ashleygwilliams]

would love to know the status on this!

[zeke]

Let's make it happen!

Do we want to first update the travis config to test on more node versions? 4, 6, 8?

[ashleygwilliams]

thanks @zeke! 4, 6, and 8 seems good to me. i'm happy to make the travis PR if you'd like as well. just lemme know!

[ashleygwilliams]

@zeke actually i just opened #70 ;) waiting on travis now

[ashleygwilliams]

@zeke ? would love to get this merged

[zeke]

I want to see this passing on node 4, 6, and 8 first. I can't edit this PR, so I've opened a followup to it: #71