fixes for v0.9.0
fixes for v0.9.0

Summary:
- add g++ to `apt-get install`
- leave opam setup to `./build-infer.sh` now that it does it for us

closes #399

Reviewed By: jberdine

Differential Revision: D3613222

fbshipit-source-id: ea8ddf7

jvillard/infer,ryoon/infer,blzq/infer,facebook/infer,facebook/infer,kageiit/infer,xennygrimmato/infer,ropas/infer,xennygrimmato/infer,jvillard/infer,jsachs/infer,xennygrimmato/infer,ryoon/infer,blzq/infer,facebook/infer,blzq/infer,jsachs/infer,ropas/infer,kageiit/infer,kageiit/infer,blzq/infer,xennygrimmato/infer,kageiit/infer,jsachs/infer,jvillard/infer,kageiit/infer,ryoon/infer,jsachs/infer,kageiit/infer,ryoon/infer,facebook/infer,facebook/infer,jvillard/infer,facebook/infer,jsachs/infer,xennygrimmato/infer,blzq/infer,xennygrimmato/infer,blzq/infer,ryoon/infer,kageiit/infer,ryoon/infer,ropas/infer,jvillard/infer,ropas/infer,facebook/infer,ropas/infer,ropas/infer,jsachs/infer,jvillard/infer,xennygrimmato/infer,jvillard/infer