bump java version to 1.7

it uses classes introduced in 1.7 - e.g. java.nio.file.Files, java.nio.file.OpenOption, java.nio.file.Path
Merge pull request #61 from matasaru/patch-1

bump java version to 1.7
Add readFully for byte[].
Merge pull request #67 from square/jw/read-fully-byte-array

Add readFully for byte[].
Test Buffer and 'Real' versions of buffered wrappers together.

This ensures that the behavior (and the semantics of that behavior) of Buffer vs. RealBufferedSource or RealBufferedSink are the same.
Merge pull request #68 from square/jw/test-improvements

Test Buffer and 'Real' versions of buffered wrappers together.
Use fully-reading helper APIs in tests.
Merge pull request #69 from square/jw/use-helper-apis

Use fully-reading helper APIs in tests.