Add missing `_download_from()` function.

hosts

@@ -218,6 +218,54 @@ _contains() {
   return 1
 }
 
+# _download_from()
+#
+# Usage:
+#   _download_from <url> [<outfile>]
+#
+# Description:
+#   Download the file at <url> and print to standard output or <outfile>, if
+#   present. Uses `curl` if available, falling back to `wget`.
+_download_from() {
+  local _downloaded=0
+  local _target_path="${2:-}"
+  local _url="${1:-}"
+
+  if [[ -z "${_url}" ]] ||
+     [[ ! "${_url}" =~ ^ftp|^http|^file|^mailto|^news|^telnet|^gopher ]]
+  then
+    return 1
+  fi
+
+  if [[ -n "${_target_path}" ]]
+  then
+    if hash "curl" 2>/dev/null
+    then
+      curl -s -L "${_url}" -o "${_target_path}" &&
+        _downloaded=1
+    elif hash "wget" 2>/dev/null
+    then
+      wget --quiet -O "${_target_path}" "${_url}" 2>/dev/null &&
+        _downloaded=1
+    fi
+  else
+    if hash "curl" 2>/dev/null
+    then
+      curl -s -L "${_url}" &&
+        _downloaded=1
+    elif hash "wget" 2>/dev/null
+    then
+      wget --quiet -O - "${_url}" 2>/dev/null &&
+        _downloaded=1
+    fi
+  fi
+
+  if ! ((_downloaded))
+  then
+    return 1
+  fi
+}
+
 # _join()
 #
 # Usage: