handle threshold_res higher than first resolution
restrict tox dependencies
init logging in autoconf
convert SRS codes to uppercase in capabilities parser
travis no longer supports python 2.5
catch and log sqlite3.OperationalError when storing tiles

this should suppress 'database is locked' errors that can happen under
high load. tiles are not stored in this case.
fix check for jpeg magic bytes
do not open cascaded responses when image format matches
return zero as timestamp when it does not present in riak cache
minimize replica count for faster tile removal in riak cache
handle exceptions when storing/removing tiles in riak
add versions option to wms service

allows to limit the WMS services to specific versions
only init libproj when requested
issue deprecation warning on python 2.5
document deprecation of python 2.5
document setuptools and update virtualenv section for windows
fixed rst markup
update CHANGES for 1.7
fix syntax error, remove unused import, upgrade dependencies for travis ci
fix logging output for tile_walker cleanups