Adding new Map visitor

Close #5
v0.2.1
Adding sourceFiles and outputFiles parameters for the Map visitor.
Adding an outputDirectory parameter for the ATUrlMap visitor.
v0.2.2
Fixing an issue in the setJSONPropertyInAST helper.
Simulating document.currentScript when executing Aria Templates in nodejs.
Debug mode option when running Aria Templates in node.js

Enabling the debug mode is especially useful for skin normalization,
so that wrong skin properties are reported.
Adding a new CheckGlobals visitor.
Adding an option to fail the build when skin normalization errors happen.
Updating dependencies
v0.2.3
Add murmurhash3 as possible hash

Close #6.
v0.2.4
Allow null visitors

Allowing null visitors can be very useful when the list of visitors can vary dependencing on some parameters.

Close #7
fix #8 Possibility to customize the application environment for ariatemplates

Close #9
Documentation content

There are two distinct targets, even if some content is mostly shared between the two for some parts:

- the user documentation, that will go to the website
- the internal documentation, for developers
Generate and deploy documentation

This commit
- configures a build process in order to generate documentation html files
- sets an automatic deploy of the generated documentation resources to the gh-pages branch done by travis after a successful build on the `stable` branch.
v0.2.5
doc Avoid mixed content errors on HTTPS

The page can be accessed via https://ariatemplates.github.io/atpackager/
and then mixed content would fail to load in modern browsers.

This changes URLs to protol-relative to avoid the issue.