glue v1.1.0

Fix for PROTECT errors when resizing output strings.

glue() always returns 'UTF-8' strings, converting inputs if in other
encodings if needed.

to() and to_data() have been removed.

glue() and glue_data() can now take alternative delimiters to { and }.
This is useful if you are writing to a format that uses a lot of braces, such
as LaTeX. (#23)

collapse() now returns 0 length output if given 0 length input (#28).