Fix parameter encoding

[robertodoering]

Hi @kaetemi,
there is an issue where some characters in the parameters don't get encoded properly, causing the oauth signature to be invalid.

This package uses the Uri.encodeComponent(param) to encode the params.
Uri.encodeComponent(param) encodes all characters except letters, numbers and -_.!~*'().
However the oauth1.0a specs define all characters except letters, numbers and -_.~ need to be percent-encoded (See https://oauth.net/core/1.0a/#encoding_parameters)

In this PR I simply replaced all occurrences of the characters that are not accounted for in Uri.encodeComponent(param) for with their percent encoded value.

I also added a changelog and raised the version number.

[robertodoering]

Hey @kaetemi, any plans to merge this?

[kaetemi]

Sorry, missed the PR mail. I'll check.

[kaetemi]

Looks OK, I'll merge it tomorrow.

Does that imply Uri.encodeComponent is not actually standards compliant?

[robertodoering]

Thanks!
Uri.encodeComponent follows the RFC 2396 standard which specifies a set of characters to encode that differs from the RFC 3986 standard that oauth1 uses.
Basically oauth1 uses an older version of the URI standard and thus require some additional characters to be percent encoded.

[kaetemi]

Aha. Interesting. I wonder why, since that appears to be a very old draft of the same standard.

[kaetemi]

Pushed to pub, thanks! :)