Change visibleText normalization in HtmlPageLoader to match WebDriver

Merge pull request #33 from DrMarcII/master

Fix bug in string normalization code.

Version 1.3.1

Prep for release to pub.

Add travis build.

Version 1.3.0

Add option to disable Shadow DOM support.

Note: this introduces breaking changes to signatures of the PageLoader constructors.

Version 1.2.6

Fixes typing for TextAreaElement.

Version 1.2.5

Adds EnsureTag annotation.

Version 1.2.4

Add eventTarget parameter to PageLoaderMouse interface.
Add Global annotation.
Cleanup formatting with dartformat.

Verison 1.2.3

Improve type() for HtmlPageLoader.

Version 1.2.2_1

Cleanup to the Lazy implementation.

Version 1.2.2

Add Lazy type for use with function fields.

Version 1.2.1

Add optional eventTarget parameter to mouse methods on HtmlPageLoader.