Loosen tilt dependency to allow any 1.x version >= 1.3.3

This change allows slim to use tilt version 1.4.0 and any future 1.x version,
which ought to be compatible, as long as tilt adheres to Semantic Versioning.

Conflicts:
	slim.gemspec
Fix indentation causing missing code block
Merge pull request #402 from mutewinter/patch-1

Fix indentation causing missing code block
erb converter
Merge branch 'master' of github.com:slim-template/slim
add comment

[ci skip]
add support for tag trailing whitespace
add tests for tag modifiers
add additional test
changes

[ci skip]
test rails 4.beta1
test against multiple tilt versions
remove uninteresting benchmarks
use newest minitest
update readme

[ci skip]
add test for erb converter
update readme

[ci skip]
require newer temple
v2.0.0.pre.9
remove unnecessary regex