Support backslash based escaping for placeholders

[santhoshtr]

The simpleParse method of parser, which get invoked if message contains only placeholders, was not supporting escaped placeholders($10)

The light weight versio of jquery.i18n when parser.js not included also has the same fix now.

Add support for that and add tests. Updated the documentation in README.md too

Fixes issue #74

[Nikerabbit]

Can you rebase this to get rid of the conflict?

[winstonsung]

Rebase needed.