Documentation Typo: "Install blobfuse driver on a kubernetes cluster" for 1.7 and 1.8

**What happened**:
The documentation for the command to use on Kubernetes 1.7 and 1.8 has a typo.

**What you expected to happen**:
The command provided for 1.7 & 1.8 should work.

**How to reproduce it**:
Review the steps under "for version v1.8 & v1.7" in https://github.com/Azure/kubernetes-volume-drivers/blob/master/flexvolume/blobfuse/README.md#2-install-blobfuse-driver-on-every-agent-vm.

**Anything else we need to know?**:
- This command:
```
kubectl apply -f https://raw.githubusercontent.com/Azure/kubernetes-volume-drivers/master/flexvolume/blobfuse/deployment/blobfuse-> flexvol-installer-1.8.yaml
```

should probably be:
```
kubectl apply -f https://raw.githubusercontent.com/Azure/kubernetes-volume-drivers/master/flexvolume/blobfuse/deployment/blobfuse-flexvol-installer-1.8.yaml
```
- The formatting for the "for version v1.8 & v1.7" section should also be fixed to be consistent with the formatting of the section for 1.9.

Start in flexvolume/blobfuse/README.md at “2. Install blobfuse driver on every agent VM,” specifically the “for version v1.8 & v1.7” section. Compare it with the v1.9 section, correct the blobfuse-flexvol-installer-1.8.yaml command and make the formatting consistent; done means the documented command and section formatting are accurate.

Written by the indexing model from the issue text.