Force move on linux systems

If the script is run as root, usually mv has an alias to ask for
overwriting. This force the overwriting.
Merge pull request #93 from colandre/master

Force move on linux systems
Minor documentation update.
Fixed a minor typo in README.md
run hostmanager before provisioners on up action

Fixes #73.
Merge pull request #95 from bkon/feature/sudo-docs

Documentation on how to set up password-less sudo for this plugin.
update vagrant dependency to 1.6.2
remove redundant initialization from Config
allow all config variables to be set at top-level and overridden per-machine

All config variables now get initialized to UNSET_VALUE so that any per-machine variables that are unspecified can fall-through to a higher-level config when the config hierarchy is merged by vagrant.

Fixes #91.
Update CHANGELOG.md
Update CHANGELOG.md
add dev version install instructions to README
Update CHANGELOG.md
update README describing new running order on 'vagrant up'
as discussed on #73.
bump for 1.5.0 release
Merge pull request #96 from pbitty/release_150

Ready for 1.5.0 release
extract old vagrant version compatibility code into util method
remove unnecessary HostsFile include
isolate core HostsFile module code into its own class
remove redundant config argument from Updater initializer