Enable Java 8 build (with a Java8 profile)

Enable Java 8 build in travis (in addition to Java7)

There's a findbugs incompatibility, so I've introduced a profile which disables it under Java8.

The profile also disables strict javadoc html checking
Support bring-your-own `MetricsRegistry` in `Bootstrap`.
Fixed broken reference for "Custom Representations"
Added an example of filtering requests.

This particular one is for filtering requests that have omitted the "Date" header field.
Modified example filter to incorporate Jersey's ExtendedUriInfo
Added an example for writing and using ServletFilters.

The request follows the example used in the Jersey filter section.
Clarified Servlet Filter text, added reference to bundled filters
Cut away some boilerplate in filter example
Corrected filter registration example to a more idiomatic approach.
Updating healthcheck example output

This now outputs in JSON instead of plain text.
Updated README to reflect version in pom.xml
Merge branch 'master' of github.com:dropwizard/dropwizard
Add Jochen Schalanda to developers in parent POM
Merge pull request #566 from reines/documentation_updates

Update example healthcheck output in the documentation
Merge pull request #568 from joschi/update-contributors

Add Jochen Schalanda to developers in parent POM
Use textual timezone designations for committers
Refactor Duration

- Initialize suffixes at one shot
- Delegate whitespace handling to the regex
- Remove redundant checking on time unit type from the regex
- Derive count and unit from the regex matching result
Refactor Size

- Initialize suffixes at one shot
- Delegate whitespace handling to the regex
- Remove redundant checking on size unit type from the regex
- Derive count and unit from the regex matching result
Merge pull request #569 from arteam/refactor_utils

Refactor Duration and Size a bit
Allow discarding any cached principal for a collection of credentials
satisfying a given predicate.