move to solidcache from a global object to the tilesource
Merge pull request #64 from mapbox/local-solidcache

Use solidcache local to the MapnikSource instance
Fix comment about use of internal_cache option
Merge pull request #65 from Vizzuality/master-internal-cache-doc

Fix comment about use of internal_cache option
use latest mapnik, eio, and hit npm directly for tests
avoid node-eio deprecation warning with newer node versions
fix repository in package.json
Accept invalid compression error message coming from mapnik < 2.2

Closes #62
Merge pull request #66 from Vizzuality/master-t62

Accept invalid compression error message coming from mapnik < 2.2
Coerce scale to a Number to make Mapnik happy

Without this, Mapnik emits `TypeError: optional arg 'scale' must be a number`.
Merge pull request #67 from mojodna/patch-1

Coerce scale to a Number to make Mapnik happy