Exclude test files from indexing.

[halftan]

May put this into command line argument, but now just use a default one.

[mkusher]

but it still needs to be fixed here #54

[halftan]

yes, I'm working on it. And also some code to make sure that cached index is used while the editing file has semantic errors.

Scenario:
Given file:

<?php
function test_function_one() {
    return new Class();
}

function test_function() {
    if (test_function_one()->{complete here}
}

And indexed file:

<?php
function test_function_one() {
    return new Class();
}

function test_function() {
}