Coding style
Catch and do nothing but reraise?  Nonsense.
Override and do nothing but call super?  Nonsense.
Correct error messages
Correct docstrings

- Invalid reStructuredText syntax
- Uninformative/misleading explanations
- Spellings and statements that don't make sense
- Lacking examples
Test documentation coverage using tox
Codec to store session+revision time
Merge pull request #2 from viobo/crawler

Crawler
Use libearth.earthreader.org domain
Merge branch 'master' of github.com:earthreader/libearth
Correct docs
Merge branch 'feedlist'
Test equality and hash of Session objects
Use libearth.org for XML namespace
RevisionSet for revisions of multiple sessions
Codec for RevisionSet
Add example code to docstring
Some concept docs and revision marking
Remove a trailing whitespace
'created' is datetime.datetime object.