semantic: wrong escape sequence in string literals  #58

As discovered in bblfsh/javascript-driver#81 (comment) and noted at bblfsh/javascript-driver#81 (comment) - bash driver does not handle string literals in semantic mode the same way as other drivers do.

On

bc = "b\nc"

//uast:String Path query results in

"@type":"uast:String","Format":"","Value":"b\\nc"

where the expected result for semantic mode would be b\ncq.