Fixed bug in the YouTrack filter. The issues should be searched for by 'resolved date', not last date of updating.

references #28
Added a new method to get the 'TaggedCommit' for the first commit.

references #28
Changing the FromTag argument to be the AllTags argument.

references #28
Making sure that each release always has an end date. Currently using the start date from the starting tag.

references #28
Searching for closed issues from the end date of the oldest release.

references #28
Fixing unit test failure.

references #28
Merge branch 'master' into issue/fromtagfirsttag
Merge pull request #35 from pvandervelde/issue/fromtagfirsttag

When specifying 'FromTag all' the issues closed for the first tag aren't included
Update README.md
Fixed issue with too many issues being included in current release
Improved tests around commit grouper