add unit tests to validate issue #97
fix Constraint::getErrors implementation

- remove presentation logic from implementation and dont filter returned errors by array_unique, business logic requires getErrors to return all existing errors, even if it contains duplicates
- make Validator::getErrors() return the same filtered result as before and apply array_unique when setting errors on Validator instance
add unit tests to validate issue #76
Use mb_strlen instead of stlen when mbstring extension is available.
split composite invalid case into independent testcases

- the composite case proved that one type check failed not all of them
replace  invalid filesystem dependent DIRECTORY_SEPARATOR  references in uri mechanics by forward slashes

- fixes failing UriResolver tests on windows systems
add unit tests to validate issue #102
dont validate draft4 required attribute when value is undefined

- fixes regression introduced by 61059b2
Add test-case for Type error messages
Fixes #104: Constraint::check() uses wrong indefinite article in ...

...error message to express the type constraint

Type::check() used a wrong indefinte article on occasion.

This has been fixed by providing a map of types and their wording so that
the correct indefinite article is used, always.

- https://github.com/justinrainbow/json-schema/pull/104
- https://github.com/composer/composer/issues/1616
Fix UriRetriever::combineRelativePathWithBasePath() does not qualify UriResolverException

Added full qualification to UriResolverException in
UriRetriever::combineRelativePathWithBasePath().
Added a test to verify that a UriResolverException is thrown when a
relative path contains more level-ups than the base path segments.
Added PHP 5.6 and HHVM to travis.yml
Merge pull request #103 from alexmmm/fix-required-property-validation

Fix required property validation
Merge pull request #100 from alexmmm/fix-basic-types-test

minor fix of BasicTypeTests
Merge pull request #98 from alexmmm/fix-constraint-errors-getter

Fix constraint errors getter
Merge pull request #99 from xanagi/multibyte_strlen

Use mb_strlen instead of strlen when mbstring extension is available.
Merge pull request #107 from Nyholm/patch-1

Added PHP 5.6 and HHVM to travis.yml
Merge pull request #101 from alexmmm/replace-directory-separator-references

replace  invalid filesystem dependent directory separator  references
Merge pull request #104 from hakre/patch-1

Constraint::check() uses wrong indefinite article in error message to express the type constraint
Merge pull request #106 from openfryer/uriretriever-uriresolverexception

Fix UriRetriever::combineRelativePathWithBasePath() does not qualify UriResolverException