Updated installation instructions

### Soft Requirements

DeepChem has a number of "soft" requirements. These are packages which are needed for various submodules of DeepChem but not for the package as a whole.

* [rdkit](http://www.rdkit.org/docs/Install.html)

* [RDKit](http://www.rdkit.org/docs/Install.html)

* [six](https://pypi.python.org/pypi/six)

* [mdtraj](http://mdtraj.org/)

* [MDTraj](http://mdtraj.org/)

* [PDBFixer](https://github.com/pandegroup/pdbfixer)

* [Pillow](https://pillow.readthedocs.io/en/stable/)

### Super easy install via pip3

### Easy Install via Conda

```bash

conda install -c deepchem -c rdkit -c conda-forge -c omnia deepchem=2.1.0

conda install -c deepchem -c rdkit -c conda-forge -c omnia deepchem=2.2.0

```

**Note:** `Easy Install` installs the latest stable version of `deepchem` and _does not install from source_. If you need to install from source make sure you follow the steps [here](#using-a-conda-environment).

**Note:** The above commands install the latest stable version of `deepchem` and _do not install from source_. If you need to install from source make sure you follow the steps [here](#using-a-conda-environment).

### Using a Docker Image

Using a docker image requires an NVIDIA GPU.  If you do not have a GPU please follow the directions for [using a conda environment](#using-a-conda-environment)

## FAQ and Troubleshooting

1. ```deepchem``` currently supports both Python 2.7 and Python 3.5, and is supported on 64 bit Linux and Mac OSX. Note that DeepChem is not currently maintained for Python 3.6 or with other operating systems. 

1. ```deepchem``` currently supports Python 3.5 and later, and is supported on 64 bit Linux and Mac OSX. Note that DeepChem is not currently maintained for Python 3.6 or with other operating systems.

2. Question: I'm seeing some failures in my test suite having to do with MKL

   ```Intel MKL FATAL ERROR: Cannot load libmkl_avx.so or libmkl_def.so.```