Maintenance version

Improvements

• added a Filterable interface on the JUnit runner to make it category-aware #256
• added a org.specs2.matcher.NoConcurrentExecutionContext trait to remove the implicit execution context for FutureMatchers
• added a BuildInfo object for each jar containing: the module name, the version, the scala version, the commit and the timestamp

Fixes

• added back the specs2.files to its proper place #258
• fixed an unsafe type conversion with mockito #260
• remove scalacheck dependency from matcherExtra module #261 (thanks to @xuwei_k)
• mockito - don't match maps and functions as equal #262 (thanks to @fwbrasil)

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