Update README.md (facebookresearch#217)

Summary:
Remove pip package install instructions and fix instructions related to GPU / INSTALL_CPP

## Types of changes

- [x] Docs change / refactoring / dependency upgrade
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)

## Motivation and Context / Related issue

## How Has This Been Tested (if it applies)

## Checklist

- [ ] The documentation is up-to-date with the changes I made.
- [ ] I have read the **CONTRIBUTING** document and completed the CLA (see **CONTRIBUTING**).
- [ ] All tests passed, and additional code has been covered with new tests.

Pull Request resolved: facebookresearch#217

Reviewed By: lw

Differential Revision: D29231442

Pulled By: adamlerer

fbshipit-source-id: db1a4e6424e6d6adfa538e3dee2e6a60962b5eaa

README.md

@@ -33,12 +33,7 @@ When running on multiple machines, they need to be able to communicate to each o
 
 ## Installation
 
-To install the latest version of PBG run:
-```bash
-pip install torchbiggraph
-```
-
-As an alternative, one can instead install the *development* version from the repository. This may have newer features but could be more unstable. To do so, clone the repository (or download it as an archive) and, inside the top-level directory, run:
+Clone the repository (or download it as an archive) and, inside the top-level directory, run:
 ```bash
 pip install .
 ```
@@ -49,7 +44,7 @@ PyTorch-BigGraph includes some C++ kernels that are only used for the experiment
 PBG_INSTALL_CPP=1 pip install .
 ```
 
-Everything will work identically except that you won't be able to run GPU training (`torchbiggraph_train_gpu`).
+Everything will work identically except that you will be able to run GPU training (`torchbiggraph_train_gpu`).
 
 
 ## Getting started