[Material] Material theme builder (#313)

* Initial version.

* Applied theming.

* Updated UI

- Updated ThemeData to baseline values

* Update readme

Update readme

* Update readme

* Update readme

* [INDEX] Adding a listing for this.

* [Material Theme Builder] PR feedback and updating for new text theme API.

* [Material Theme Builder] More PR feedback.

* [Material Theme Builder] Adding to Travis.

* [Material Theme Builder] Rebase conflicts.

* [Theme Generator] Adding 1 link to the readme.

Co-authored-by: yasmineevjen <yasmineevjen@users.noreply.github.com>

tool/travis_flutter_script.sh

@@ -33,6 +33,7 @@ declare -ar PROJECT_NAMES=(
     "infinite_list" \
     "isolate_example" \
     "jsonexample" \
+    "material_theme_builder" \
     "place_tracker" \
     "platform_design"
     "platform_view_swift" \