Fixes issues with ArrayValue

Addresses:
* Issue with list assignment of ArrayValue
* Issue with returning ArrayType values by improving handling of
O8 data

Adds 'interop' test in test_parameter_values to ensure returns are the
same with in-memory or persisted
Fixes issue in CategoryType when setting with None
Merge pull request #56 from blazetopher/pval_fixes

ParameterValue Fixes
Buildout 2.0
Adds precison to ParameterContext
Merge pull request #57 from lukecampbell/precision

Adds precison to ParameterContext
Ensures PersistedStorage returns either atleast_1d or scalar

Makes certain that the value(s) returned by the PersistedStorage are either a scalar value or at least a 1d numpy array

Also adds interop parameter_values test for category value
Merge pull request #58 from blazetopher/get_val_fix

Ensures PersistedStorage returns either atleast_1d or scalar
Adds new files supporting the refactored nosetests framework.
Adds time axis to 'time' parameter.
Continues migration from test_coverage_basics.
Continues migration from test_coverage_basics.

Replaces uppercase parameter names to lowercase in tests.
Comments out migrated tests in test_coverage_basics.
Removes working directory if exists.
Completes migration from test_coverage_basics.py

test_slice_and_dice omitted from tests due to suspected duplication with test_get_by_slice.
Adds get_props decorator function

Adds get_props() decorator function and TESTING_PROPERTIES class dictionary to enable subclasses to provide properties on a class-wide and test-by-test basis.  This allows the tests defined in CoverageIntTestBase to remain generic and flexible.
Adds tests and minor cleanup.

Adds test for checking the list_parameters() function.
Refactors assertions using SimplexCoverage to AbstractCoverage.
Adds override for empty coverage test.

Added override for test_get_by_slice.