Only add MBID to requestParams if present as it will cause problems
when creating the request signature
Add latest version details, new contributor and make contributors more visible.
Treat undefined and null parameters as blank in signatures.
Remove content-length for GET requests.

Partial revert of 693f893. Content-Length was required because
the data was accidentally being sent in the body of GET requests.
This should only be done on POST.
Bump version number -> 0.8.3
Merge branch 'hotfix/v0.8.3'
Merge 0.8.3 and 0.8.2 details

0.8.2 was never officially released.