Don't pollute the START variable

[bronson]

It's bad to leak the START variable into the user's environment so do the install steps in a subshell.
Also, don't try to install npm if the node install fails.

This change is mostly indentation, here's the git diff -b:

@@ -36,21 +36,25 @@ nvm()
         nvm help
         return;
       fi
-      START=`pwd`
-      mkdir -p "$NVM_DIR/src" && \
+      if (
+        mkdir -p "$NVM_DIR/src" &&
       cd "$NVM_DIR/src" && \
       wget "http://nodejs.org/dist/node-$2.tar.gz" -N && \
       tar -xzf "node-$2.tar.gz" && \
       cd "node-$2" && \
       ./configure --prefix="$NVM_DIR/$2" && \
       make && \
-      make install && \
+        make install
+        )
+      then
       nvm use $2
       if ! which npm ; then

         echo "Installing npm..."
         curl http://npmjs.org/install.sh | sh
       fi
-      cd $START
+      else
+        echo "nvm: install $2 failed!"
+      fi
     ;;
     "deactivate" )
       if [[ $PATH == *$NVM_DIR/*/bin* ]]; then

[creationix]

Not sure why this wasn't closed, but I merged this in a while back.