Race condition while running tests with bem server

[narqo]

How to reproduce.

With bem-core:

1. clone the repo
2. npm i && bower-npm-install
3. bem server

Open http://localhost:8080/desktop.specs/i-bem/spec-js+browser-js+bemhtml/_spec-js+browser-js+bemhtml.html in browser. See the blank page instead of mocha's test's results.

[narqo]

Was hardfixed in #57 but seems to be lost after v0.5