Allow to define custom IP resolver
Update README.md

Add description of custom IP resolver
 #44 Handle destroyed machines in update_file

Keep track of machines that have been destroyed (they have a nil id).
Do not include them when updating the hosts file.

Since it is impossible to match on id, this is accomplished by matching
the exact ip / hostname / alias.  If any of these have been altered
since the entry was created the entry will not be removed from the hosts
file.

Potentially, this could be relaxed to only match on ip / hostname pairs.
Properly convert provider command option to symbol
Use :SystemRoot to detect Windows, including git-bash. Also use :Windir to ensure we get correct hosts file path
Merge pull request #45 from bdcribbs/fix/44

Handle destroyed machines in update_file.  Fixes #44
Merge pull request #46 from emyl/provider-to-sym

Properly convert provider command option to symbol
Merge sevos pull/15 into master

Merge branch 'enable_using_private_ips_from_aws' of
https://github.com/sevos/vagrant-hostmanager into master.

Conflicts:
	lib/vagrant-hostmanager/config.rb
	lib/vagrant-hostmanager/hosts_file.rb
Merge branch 'sevos-enable_using_private_ips_from_aws'
Merge pull request #49 from Tpbrown/git-bash-windows

Support Cygwin and MinGW on Windows.  Fixes #24
fix indentation (using spaces instead of tabs)
elevate privileges in Windows host if necessary
use rbconfig for detecting Windows