Fixing OAuth support as Atlassian provider only supports RSA-SHA1

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Atlassian OAuth only provides RSA-SHA1 (at least in the cloud version). This requires a new version of request module, the old version doesn't support RSA-SHA1.

But seems everything else is still working.

Also oAUTH module is not needed, so removed it.

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Fixes #61 and #9

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@pranavv See https://github.com/steves/node-jira/issues/122 - There is a fork, where this commit was added https://github.com/jira-node/node-jira-client