Fix issuetype calls adding URL escaping
Fix issuetype calls adding URL escaping

It is valid within JIRA to have issue types with spaces (for example we use
"Pro-Active Task") however the issuetype variable is not escaped prior to
formatting into the uri string.

This fix imports "net/url" and escapes all inclusions of issuetype into uri.
The only other variables formatted into uri are c.endpoint and issue which
shouldn't contain special characters.

mikepea/go-jira