Shell Script – Extract Text Between Triple Single Quotes

I have the following in a file

description: '''
        This rule forbids throwing string literals or interpolations. While
        JavaScript (and CoffeeScript by extension) allow any expression to
        be thrown, it is best to only throw <a
        href="https://developer.mozilla.org
        /en/JavaScript/Reference/Global_Objects/Error"> Error</a> objects,
        because they contain valuable debugging information like the stack
        trace. Because of JavaScript's dynamic nature, CoffeeLint cannot
        ensure you are always throwing instances of <tt>Error</tt>. It will
        only catch the simple but real case of throwing literal strings.
        <pre>
        <code># CoffeeLint will catch this:
        throw "i made a boo boo"

        # ... but not this:
        throw getSomeString()
        </code>
        </pre>
        This rule is enabled by default.
        '''

with several other things in this file.

I extract this part in my shell script via sed -n "/'''/,/'''/p" $1 (where $1 is the file).

This gives me a variable with the content as one liner

description: ''' This rule forbids throwing string literals or interpolations. While JavaScript (and CoffeeScript by extension) allow any expression to be thrown, it is best to only throw <a href="https://developer.mozilla.org /en/JavaScript/Reference/Global_Objects/Error"> Error</a> objects, because they contain valuable debugging information like the stack trace. Because of JavaScript's dynamic nature, CoffeeLint cannot ensure you are always throwing instances of <tt>Error</tt>. It will only catch the simple but real case of throwing literal strings. <pre> <code># CoffeeLint will catch this: throw "i made a boo boo" # ... but not this: throw getSomeString() </code> </pre> This rule is enabled by default. '''

How can I now extract the part between the ''' ?

Or is there even a better way to retrieve it from the multiline file ?

I'm on Mac El Captain 10.11.2 and GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin15)