Prevent loading templates out of the search paths

This check prevents someone to use a relative path to a template in a directory outside the search paths. For example: "../../something/bad.html".

I am using nunjucks in a web service where users can edit their own templates and of course I don't want to let them to find a system file or use a template of another user.
fix express test
Merge pull request #40 from gimenete/patch-1

Prevent loading templates out of the search paths
Merge remote-tracking branch 'origin/master'
update version
fix {% raw %} block
Pass frame to _compileExpression
Fix frame lookups for falsy values
Regenerate browser files
Merge pull request #42 from hiidef/master

Two small bugfixes
minor cleanup
fix using precompiled templates (fixes #43)
Fix syntax which causes errors with YUICompressor
Merge pull request #45 from fooby/master

Remove reserved keywords as property names
use withPrettyErrors when precompiling
type with error handling
Normalize the FileSystemLoader paths to ensure proper path separators on windows.
(for running the unittests in windows)
Fix int/float filters returning a value of undefined (or the default value, if provided) when passed a string containing "0".
Merge pull request #48 from fooby/master

Fix for int/float filters returning "undefined" when passed a string of "0"
fix error when using super(), and track runtime line/col number information