Use badges from shields.io in README

I've found that the badges provided by shields.io look much better than the default ones provided by Travis.
update to AsciidoctorJ 1.5.0
add mojavelinux to list of contributors
Merge pull request #106 from aalmiray/patch-1

Use badges from shields.io in README
don't embed stylesheet when generating XHTML for site
resolves #103 support .adoc extension in addition to .ad
resolves #109 add configuration for gemPath and requires
switch gemPath to a String
Removed method causing failure
Fixes #112

Project was already set, added rootDir and getters / setters for properties that needed them.
Forgot to add the property names for maven.
Fixes #111

gemPath, unless otherwise configured, will always be an empty string. I think that's correct.
Infrastructure for #94

I'd like a more automated way of testing snapshots, if anyone has some ideas.
Resolves #67

We're adding more synchronizations, if you need to add others, you can do so in the plugin configuration. We're pulling everything from sourceDirectory that isn't an AsciiDoc document (.ad, .adoc, .asciidoc) and copying it to the output directory.
Resolves #67

This is a better way to do that.
resolves #93 properly handle attribute values

- recognize null as an empty string (yes, Maven isn't that smart)
- recognize "true" and "false" as Boolean values
- update tests to cover these scenarios
resolves #115 issue warning if GEM_HOME resolves to unexpected external path
#14 maybe this helps for integration-tests
Merge branch 'it_test'

Resolves #14
Merge pull request #116 from mojavelinux/issue-115

resolves #115 issue warning if GEM_HOME resolves to unexpected external path