Add basic support for ANSI color escape codes.

Nim's `terminal` library provides ANSI terminal escape support, but
only when writing directly to a File handle. This commit adds the
`term{FG,BG}` procedures and `termReset` constant to help with embedding
ANSI escape codes in string data.

cliutils.nim

@@ -1,4 +1,4 @@
-import docopt, json, osproc, posix, nre, streams, strtabs, unicode
+import docopt, json, osproc, posix, nre, streams, strtabs, terminal, unicode
 import os except sleep
 import strutils except toUpper, toLower
 
@@ -171,3 +171,15 @@ proc daemonize*(pidfile, si, so, se: string, daemonMain: proc(): void): Pid =
     daemonMain()
 
   return pid1
+
+proc termFG*(color: ForegroundColor, bright, bold = false): string =
+  var colorVal = ord(color)
+  if bright: inc(colorVal, 60)
+  return "\e[" & $colorVal & (if bold: ";1" else: "") & "m"
+
+proc termBG*(color: BackgroundColor, bright, bold = false): string =
+  var colorVal = ord(color)
+  if bright: inc(colorVal, 60)
+  return "\e[" & $colorVal & "m"
+
+const termReset* = "\e[0;m"