Merge remote 'nre' into add-nre

* nre-proj/master: (132 commits)
  Change to options module
  Reweave readme
  Better handle errors
  Update documentation
  Change flags to inline
  Improve performance
  Add tests for empty or non-empty match
  Fix skipping an empty match at the end
  Add longer flags
  Fix getinfo overflows
  Use docweave
  Convert readme to RST
  Fix result shadowing warning
  Throw an exception when replacing with a nil value
  Fix potential buffer overflow
  Fix zero-length matches for multibyte characters
  Make splitting an empty string give 1 empty result
  Change endpos to inclusive
  Change endpos default from -1 to int.high
  Change capture upper bounds to inclusive
  ...

lib/impure/nre/test/escape.nim

@@ -0,0 +1,7 @@
+import nre, unittest
+
+suite "escape strings":
+  test "escape strings":
+    check("123".escapeRe() == "123")
+    check("[]".escapeRe() == r"\[\]")
+    check("()".escapeRe() == r"\(\)")