Only ship the necessary libs in the gem artifact (#148)

The gem artifact is not the ideal place to ship examples, contributing
docs, a rake file and various hidden files. This will greatly reduce the
size of the installed gem artifact and speed up installs on systems with
malware scanners. This drops the compressed gem size.

Signed-off-by: Tim Smith <tsmith@chef.io>

.travis.yml

@@ -2,9 +2,10 @@ language: ruby
 rvm:
   - 1.8.7
   - 1.9.3
-  - 2.2.6
-  - 2.3.3
-  - 2.4.0
+  - 2.2.10
+  - 2.3.8
+  - 2.4.5
+  - 2.5.3
   - jruby-1.7.26
   - jruby-9.1.8.0
 before_install:

rbvmomi.gemspec

@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.license  = 'MIT'
 
   spec.bindir = 'exe'
-  spec.files  = `git ls-files -z`.split("\x0").reject { |f| f.match(/^test\//) }
+  spec.files  = %w{LICENSE README.md vmodl.db} + Dir.glob("{lib,exe}/**/*")
   spec.executables << 'rbvmomish'
 
   spec.add_runtime_dependency('builder', '~> 3.0')