Replace Solve with RubyGems in Vagrant version checking

`Solve::Constraint` doesn't support pre-release version numbers[1], so
replace it with `Gem` classes while waiting for a fix.

Fixes #97

[1]: https://github.com/RiotGames/solve/issues/29
Compatibility with vagrant-aws v0.4.0

Next vagrant-aws release will remove its custom TimedProvision class and
use only the standard Builtin::Provision instead.

To support both old and new versions of the plugin, check if the
TimedProvision class is defined before using it.
Merge pull request #100 from tmatilai/vagrant-version-check

Replace Solve with RubyGems in Vagrant version checking
Merge pull request #99 from tmatilai/aws-0.4

Compatibility with vagrant-aws v0.4.0
update changelog
bump version to 1.4.0.dev
bump master berks dep to beta3
Bump version to dev1
RiotGames/vagrant-berkshelf -> berkshelf/vagrant-berkshelf
Merge pull request #121 from berkshelf/update-org-locs

Update organization for berkshelf
Fix relative path handling in cache_file
remove accidentially added "require pathname"
Use File.expand_path relative to global_config.root_path
Do it in validate, since that's the first time we have access to global_config (I think)
bump tested gem requirements

change this from a single string to an array of requirements
Merge pull request #128 from berkshelf/update-tested-requirement

bump tested gem requirements
fix tests to include reference to env.root_path in vslidate phase
Merge pull request #129 from issacg/125_relative_paths

125 relative paths
bump tested requirement