Merge pull request #26 from gpratt/master

fixed bug with merge function
add force_merge_fields kwarg, plus test; fixes #27
Merge branch 'master' of https://github.com/daler/gffutils
remove redundant check for start/end
count_features_of_type can count all features
(should be appended to last commit)
new add_relation method. fixes #28
__str__ calls new __unicode__
include example data in sdist upload to PyPI
Merge branch 'master' of https://github.com/daler/gffutils
stringify version
add flybase conversion script
add UrlIterator - fetch files from http, https, ftp...
Merge pull request #30 from mladvladimir/urliterator

add UrlIterator - fetch files from http, https, ftp...
fixed bug in merge_attributed, added tests to cover regression in the future