Fix #780 so that fill works with all aggregates
Refactor data_test.go to use Test* function names

Refactor integration/data_test.go to use Test* names for the tests
and remove the TestAll test case, which uses reflection to iterate
over all test functions.  Also, change the two SingleServerSuite
test functions in this file to DataTestSuite functions.

The DataTestSuite now conforms to standard Go / gocheck test
conventions.  Individual tests can be run.  Groups of tests can be
run by specifying patterns.  E.g.,

make integraton_test only=DataTestSuite

...will run all tests in data_test.go.  Or,

make integration_test only=DataTestSuite.Test.*Histogram

...will run all histogram related tests.

See the gocheck documentation for further details.
Merge remote-tracking branch 'refs/remotes/origin/pr/920'

Conflicts:
	integration/data_test.go