chore: update ruby & bundler version for CI

* bundler 1.12.5 breaks with current version of dependencies
  (NoMethodError: undefined method `[]' for nil:NilClass)
* vagrant-2.2.17 requires ruby version ~> 2.5, < 2.8

.travis.yml

@@ -1,10 +1,10 @@
+---
 language: ruby
 rvm:
-  - 2.2
-  - 2.3
-  - 2.4
   - 2.5
+  - 2.6
+  - 2.7
 install:
-  - gem install -v 1.12.5 bundler
-  - bundle _1.12.5_ install --jobs=3 --retry=3
+  - gem install -v 1.16.2 bundler
+  - bundle _1.16.2_ install --jobs=3 --retry=3
 script: "bundle exec rake ci"

Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 
 group :development do
-  gem 'vagrant', git: 'https://github.com/mitchellh/vagrant.git'
+  gem 'vagrant', git: 'https://github.com/mitchellh/vagrant.git', branch: 'main'
   gem 'guard'
   gem 'guard-rspec'
   gem 'rb-inotify'
@@ -11,7 +11,7 @@ group :development, :test do
   gem 'rake', '~> 10.4.2'
   gem 'rspec', '~> 3.5.0'
   gem 'coveralls', '~> 0.7.2', require: (ENV['COVERAGE'] == 'true')
-  gem 'vagrant-spec', git: 'https://github.com/mitchellh/vagrant-spec.git'
+  gem 'vagrant-spec', git: 'https://github.com/mitchellh/vagrant-spec.git', branch: 'main'
 end
 
 group :plugins do

README.md

@@ -1,7 +1,3 @@
-🟢 We plan to support and maintain vagrant-lxc, as well as clean it up.<br/>
-🟢 Please feel free to contribute Issues and pull requests.<br/>
-🟢 P.S: Thanks [Fabio Rehm](https://fabiorehm.com) for the amazing initial project.
-
 # vagrant-lxc
 
 [![Build Status](https://travis-ci.org/fgrehm/vagrant-lxc.png?branch=master)](https://travis-ci.org/fgrehm/vagrant-lxc) [![Gem Version](https://badge.fury.io/rb/vagrant-lxc.png)](http://badge.fury.io/rb/vagrant-lxc) [![Code Climate](https://codeclimate.com/github/fgrehm/vagrant-lxc.png)](https://codeclimate.com/github/fgrehm/vagrant-lxc) [![Coverage Status](https://coveralls.io/repos/fgrehm/vagrant-lxc/badge.png?branch=master)](https://coveralls.io/r/fgrehm/vagrant-lxc) [![Gitter chat](https://badges.gitter.im/fgrehm/vagrant-lxc.png)](https://gitter.im/fgrehm/vagrant-lxc)

scripts/pipework

@@ -390,7 +390,7 @@ else
       ;;
     "")
       if installed ipcalc; then
-        eval "$(ipcalc -b $IPADDR)"
+        eval $(ipcalc -b $IPADDR)
         ip netns exec "$NSPID" ip addr add "$IPADDR" brd "$BROADCAST" dev "$CONTAINER_IFNAME"
       else
         ip netns exec "$NSPID" ip addr add "$IPADDR" dev "$CONTAINER_IFNAME"