Extract Parsers to separate classes

[supremebeing7]

There is already the Toggl::IssueKeyParser, but there should probably be one parser for a Toggl entry that returns all of the attributes needed. Currently, a lot of the parsing happens in JIRA::WorkLogger, but this is bad. WorkLogger should be agnostic of all parsing - it should receive just an array of time entries with the attributes it needs (description, comment, issue key, start time, duration).