reformat docs

* configure: clean spaces, tab's
* .gitignore: ignore the subfolder "build", build/binary files
* README.md: [related link](https://github.com/denji/hhvm/commit/9fa7fcba90f3e0aacf44929385f91aad762e9ac3?short_path=04c6e90#diff-04c6e90faac2675aa89e2176d2eec7d8)