Engine refacto with most of the features available

This is a follow up of the v0.8.5-alpha.1 with most of the previous features available (i.e. word splitting, distinct fields).

It is always 3x to 10x faster than the previous core engine algorithm (I even see 27x on specific queries).

Refacto of the search engine

We rewrote the full underlying system to gather performances and reduce the amount of work necessary to answer queries resulting in massive query time reduction (seen x3 to x30 times faster). This is an alpha release, don't use this version in production or anything that need stability.

The exposed port change

We now expose the port 7700 instead of the 8080, this way we avoid conflicts with common existing TCP servers (i.e. node).

A brand new update display

We change the output format of the updates, you can read more about that in #350 and #354.

Reduce the number of dependencies

We no longer need the libssl runtime dependency which, as you probably already know, is one of the hardest dependency to install...

Make the engine accept updates asyncly

Now you will be able to send updates to the HTTP server without having to wait for it to process anything but the body parsing (#340).

The big breaking release

This is the first big release of MeiliSearch and it breaks many HTTP APIs but don't worry the documentation is up to date.