Fix sed commands (#2071)

In GNU `sed`, the `-iEe` argument is equivalent to `--in-place=Ee`, which would create `~/.profileEe` as backup of `~/.profile` if the command executed successfully. However, because the `e` is no longer being processed as an expression argument, `sed` does not correctly join the expressions and exits with `sed: -e expression #2, char 10: unexpected }`.

The intent is to use extended regex, perform the changes in-place, and use a series of expressions, so `-Ei -e` is used instead.

README.md

@@ -239,7 +239,7 @@ easy to fork and contribute any changes back upstream.
          ~~~bash
          # the sed invocation inserts the lines at the start of the file
          # after any initial comment lines
-         sed -iEe '/^([^#]|$)/ {a \
+         sed -Ei -e '/^([^#]|$)/ {a \
          export PYENV_ROOT="$HOME/.pyenv"
          a \
          export PATH="$PYENV_ROOT/bin:$PATH"
@@ -253,7 +253,7 @@ easy to fork and contribute any changes back upstream.
       - **If your `~/.bash_profile` sources `~/.bashrc` (Red Hat, Fedora, CentOS):**
 
          ~~~ bash
-         sed -iEe '/^([^#]|$)/ {a \
+         sed -Ei -e '/^([^#]|$)/ {a \
          export PYENV_ROOT="$HOME/.pyenv"
          a \
          export PATH="$PYENV_ROOT/bin:$PATH"