Package uritemplates is a level 3 implementation of RFC 6570 (URI
Template, http://tools.ietf.org/html/rfc6570).
uritemplates does not support composite values (in Go: slices or maps)
and so does not qualify as a level 4 implementation.
Expand parses then expands a URI template with a set of values to produce
the resultant URI. Two forms of the result are returned: one with all the
elements escaped, and one with the elements unescaped.