Closes #253.

I simplified the implementation of this class a bit, and extended the unit tests to include a case that was causing problems before.
Code syntax
Fixed unused parameter
Merge pull request #254 from standage/master

Closes #253.
Fixes ill-formatted API documentation for GtSetSourceVisitor
Vanity edit
Merge pull request #257 from standage/cont

Vanity edit
Merge pull request #256 from standage/docs

Fixes ill-formatted API documentation for GtSetSourceVisitor
disable some tests on Mac
update CHANGELOG
Merge pull request #258 from satta/mactests

disable some tests on Mac
Merge pull request #259 from satta/prerelease

update CHANGELOG
disable gt_seqlensort test on Mac
Merge pull request #260 from ggonnella/no_seqlensort_test_on_mac

disable gt_seqlensort test on Mac
update html
Merge pull request #261 from gordon/http

update html
update paper reference on website
Merge pull request #262 from satta/www

update paper reference on website
update release date
version bump

Closes #245.