Allow queries to be specified as a dict.

Adds the ability for the queries parameters to be defined as a mapping
of zoom level to the query.  Undefined zoom levels are assumed to be null.
Allow S3 policy to be specified in config

Adds an optional 'policy' field to the S3 configuration allowing specific
permissions to be specified. The default is 'public-read'.
Return a transparent tile if coord is out of bounds.
Add 'scale factor' option to Mapnik image provider

Adds the optional 'scale factor' argument in the config for Mapnik's
image provider. Allows a TileStache layer to be configured for retina.
Properly document 'scale factor' option.

Remove improper underscore
Fix UtfGridComposite to work with latest TileStache
Merge pull request #167 from danzel/fix-utfgridcomposite

Fix UtfGridComposite to work with latest TileStache
Merge pull request #190 from mattmakesmaps/master

Update .travis.yml To Fix Broken Test Build
correct documentation for layer_id_key, layer_index
Add responding to "/favicon.ico"
Remove unnecessary dict update.
Merge pull request #157 from jwass/scale_factor

Add 'scale factor' option to Mapnik image provider
fix Pillow dependency
Merge pull request #196 from slafs/PILfix

fix Pillow dependency
Merge pull request #195 from garnertb/minutia

Remove unnecessary dict update.
Merge pull request #194 from ypyf/master

Add responding to "/favicon.ico"
Revert "Add responding to "/favicon.ico""
Merge pull request #197 from TileStache/revert-194-master

Revert "Add responding to "/favicon.ico""
enable "cache lifespan" in Redis cache
Is now capable to read config file from http resource (same as Mappnik.py)