Don't exit out of piped loop

Can cause the stdin of cat to close too soon causing:

  echo: write error: Broken pipe

Fixes #97

libexec/rbenv-version-file-read

@@ -7,13 +7,18 @@ VERSION_FILE="$1"
 if [ -e "$VERSION_FILE" ]; then
   # Read and print the first non-whitespace word from the specified
   # version file.
+  version=""
   while read -a words; do
-    version="${words[0]}"
-    if [ -n "$version" ]; then
-      echo "$version"
-      exit
+    word="${words[0]}"
+    if [ -z "$version" ] && [ -n "$word" ]; then
+      version="$word"
     fi
   done < <( cat "$VERSION_FILE" && echo )
+
+  if [ -n "$version" ]; then
+    echo "$version"
+    exit
+  fi
 fi
 
 exit 1