bug: repeated string_content nodes

[calebdw]

Describe the bug

@amaanq,

See related comment: #237 (comment)

Creating an issue so it doesn't get lost---the new string_content regex is creating a parse tree with repeated nodes (should just be a single node, see below for examples).

Perhaps this should be moved to the scanner? It solves the precedence and parse issues in one go...

Steps To Reproduce/Bad Parse Tree

'#([\w().,;]|[`]{1})$#'

              (string
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (string_content))

'#^([\w().,;]|\\\--[\w]|[]{1})#'

              (string
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (string_content)
                (escape_sequence)
                (string_content)
                (string_content))

Expected Behavior/Parse Tree

'#([\w().,;]|[`]{1})$#'

              (string
                (string_content))

'#^([\w().,;]|\\\--[\w]|[]{1})#'

              (string
                (string_content)
                (escape_sequence)
                (string_content))