Build: Lock acorn to v4.0.4

[kaicataldo]

See

• acorn@4.0.5 breaks eslint acornjs/acorn#496
• Strange eslint hangs on 4.0.5 release acornjs/acorn#497

[puzrin]

Note, 4.0.7 not hangs, but still only partially fixed another bug acornjs/acorn#500 (comment). After forced updates i still see error report in eslint. It worth keep espree on 4.0.4 a bit more.

[puzrin]

Update: 4.0.8 fixed things (see link above for details).

As author says, technically that fix is not perfect and should be improved. But 4.0.4 had the same problem. So now 4.0.8 should be not worse than 4.0.4.

[gyandeeps]

Apparently 4.0.8 has some other issues: #316

[puzrin]

Sorry for confusion, i meaned only very specific case like [ (G = s), F = G ], which could be missed in tests.

[nzakas]

Just a reminder: dependency changes should be "Upgrade:" or "Update" (in this case). This change is unrelated to the build.