Fix CMake commands in README
Fix CMake commands in README

Summary:
Remove bogus `configure` argument from cmake commands which is likely an
artefact from automake migration. The correct invocation of CMake is

```
cmake [<options>] {<path-to-source> | <path-to-existing-build>}
```

Reviewed By: Orvid

Differential Revision: D9721030

fbshipit-source-id: 95da844d3292cbf2acbec85753499f3603567e08

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly