* json-sort-keys:
  Add support for sorting json keys

Add `jsonSortKeys` property to HttpMapperProperties.

Fixes gh-498

Minoir polish for wrapping at 90 and tabs instead of spaces.

This commit reviews the How-to part of the Spring boot doc,
fixing mostly typos.

See gh-521

It is sufficient for most purposes (e.g. the ones PropertieLauncher needs)
to only read the META-INF directory (not the whole file tree). So a quick
fix is to make META-INF a special case when initializing non-recursive
entries.

Fixes gh-520

When repackaging an archive, the files in the resulting lib directory
must be zip files. If they're not zip files, the resulting archive
may fail to run (#324).

The previous approach was to consider an artifact's type when deciding
whether or not it should be packaged. The type is a string and, while
there are a number of well-known values, it can essentially be anything.
This caused a problem with an artifact incorrectly being identified as
being unsuitable for inclusion (#489).

This commit changes the approach. Rather than looking at an artifact's
type, it looks at the first four bytes  of the archive's file. Only if
these header bytes matche that of a zip file is the artifact included.
This is a better match for the requirement that all files in lib be zip
files.

Fixes #489

Fixes gh-518

Fixes gh-500

Fixes gh-507

Fixes gh-499

Change working since test dependencies cannot easily be replaced.

Remove quote-marks from internal documentation links and instead favor
italics.

* docs:
  Review first 8 parts of the doc

This commit mostly fixes typos but also improves slightly specific
areas, adding links when it make sense.

See gh-499

Currently Spring Boot fails in Java 1.6 on Mac OS X due to the
"tools.jar" being integrated into classes.jar in the Apple version of
Java 6.

Apple fixed this with Java 7, but we should still support Java 6. We had
to roll back to maven-plugin-plugin 3.1 to make this work with Java 6
and 7.

All tests pass with Java 6 and Java 7.

Fixes gh-492

Fixes gh-495

Remove README files that have been since been migrated to the reference
documentation. Also updated remaining markdown files to asciidoctor to
save having a mix of different formats.

Fixed gh-503

Port Add Maven example for Tomcat 8 from markdown to asciidoc.
(originally from commit 15372cb7)

Port documentation originally added in commit b56bd0a1