fix README.md

man yum says the following about localinstall:

```
        * localinstall rpmfile1 [rpmfile2] [...]
           (maintained for legacy reasons only - use install)
```

and

```
       localinstall
              Is  used  to  install  a  set of local rpm files. If required the enabled
              repositories will be used to resolve dependencies. Note that the  install
              command  will  do  a  local install, if given a filename. This command is
              maintained for legacy reasons only.
```


I also changed b tags to ** which is bolding in markdown. I think that strong should be used instead of b anyway.