Support following relative redirects
JavaDoc for TestHttpClient

Fixes #501
Update JavaDoc for changes.
Split manual.js into more files and apply grunt-js.

src/assets/js files are thematically splited.
grunt-js plugin is used in order to combine js files into one all.js.
grunt-js plugin is used in order to minify combined js file into
all.min.js.
IMPORTANT: because grunt-js has incompatible reference to google's
guava, so minifyjs.gradle build file is executed as separate GruntBuild
file.

HTML files for manual as well as Javadoc API reference to all.min.js
file.
Remove grunt-js reference from ratpack-manual build.
Merge branch 'master' of https://github.com/zedar/ratpack
Remove grunt-js reference from ratpack-manual.