message: improve README.md
  Closes:
  Approved by: junkil-park
diff: There are three experimental scripts in this folder.
  -1. `install-dotnet.sh` installs Dotnet Core.
  -2. `install-boogie.sh` installs the latest version of Boogie from nuget.org.
  -3. `install-z3.sh` installs a specific version of Z3.
  +- `install-dotnet.sh` installs Dotnet Core.
  +- `install-boogie.sh` installs a specific version of Boogie from nuget.org.
  +- `install-z3.sh` installs a specific version of Z3.
  -`install-dotnet.sh` must be executed before `install-boogie.sh`. There is no other dependency.
  -`install-dotnet.sh` installs the Dotnet Core SDK and the `dotnet` tool. The installation could fail
  -on your machine because a few directories must be writable by your user account. You should
  -change the ownership of these directories to your user.
  - sudo chown -R $(whoami) /usr/local/bin /usr/local/lib /usr/local/sbin
  -And make sure that your user has write permission.
  - chmod u+w /usr/local/bin /usr/local/lib /usr/local/sbin
  +# Installation steps
  -The commands `boogie` and `z3` should be in your path once these scripts have finished successfully.
  +1. The installation of Dotnet Core requires a few directories to be writable by your
  + user account. You should change the ownership of these directories to your user.
  + - sudo chown -R $(whoami) /usr/local/bin /usr/local/lib /usr/local/sbin
  + Then make sure that your user has write permission.
  + - chmod u+w /usr/local/bin /usr/local/lib /usr/local/sbin
  +2. ./install-dotnet.sh
  +3. ./install-boogie.sh
  +4. ./install-z3.sh
  -To check the location of the tools installed, use the following commands:
  +Troubleshooting:
  +On bash, the commands `boogie` and `z3` should be in your path once these scripts
  +have finished successfully. On zsh, you may have to add /Users/$(whoami)/.dotnet/tools
  +manually to $PATH.
  +
  +# Setting environment variables for running Move Prover
  +
  +The Move Prover looks for Boogie and Z3 executables in the environment variables BOOGIE_EXE
  +and Z3_EXE, respectively. To run Boogie/Z3 on the Boogie files generated by the tests of
  +this crate, these environment variables must be set. To check the location of the tools,
  +use the following commands:
  ```
  which boogie
  which z3
  @@ -21,12 +32,7 @@ which z3
  type -p boogie
  type -p z3
  ```
  -
  -The Move Prover looks for Boogie and Z3 executables in the environment variables BOOGIE_EXE
  -and Z3_EXE, respectively. To run Boogie/Z3 on the Boogie files generated by the tests of
  -this crate, these environment variables must be set. To set these environment variables,
  -execute the following at the command-line after running the installation scripts described
  -above:
  +The following commands should set BOOGIE_EXE and Z3_EXE appropriately.
  ```
  export BOOGIE_EXE=/Users/$(whoami)/.dotnet/tools/boogie
  export Z3_EXE=/usr/local/bin/z3
  