Lazy Indexing #60

Here's the idea. Instead of doing mass reindex in project root there could be something like a lazy index. On the first completion, we could collect files and classes only (which should be much faster than a full index), and then when doing completion inside the file index missing related files. So if class A uses object of class B then index class B etc. Hopefully, it's clear what the idea is.

With that feature, we could have full completion in any project without needs for full reindex.

Just to give you some figures, reindex in one of my projects:

$ \time -f %es padawan generate
...
74.82s

In the same project:

$ \time -f %es ag --php '^class.*$'
...
0.98s

It would be probably slower in pure PHP, but still should be faster than full reindex.

How feasible you think it is?