bitfinex use v2 api, sequence IDs

[evan-coygo]

for #236

• update to v2 bitfinex websocket API
• add config call to get sequence IDs included in each message
• increase default book depth from 100 to 250

[evan-coygo]

@bmancini55 requested changes made. It now includes a config flag for timestamps and parses out the timestampMs for each message.

I added the checksum config flag as well, but it arrives in its own separate message so I wasn't sure exactly how you'd want to handle that. For example does it just get sent passed to the client as its own empty l2Update that includes on the checksum and no bids or asks data?

[evan-coygo]

@bmancini55 alright I removed the checksum config flag

[evan-coygo]

@bmancini55 alright pushed up requested fixes

[bmancini55]

Thanks!