Allows append_parameter after coverage creation

Can now call append_parameter against a coverage at any time and the
parameter will be fully formed and functional.
The domain of the coverage will be applied to the parameter.
Adds test coverage for append_parameter.
Adds parameter exists check and test coverage.

Modifies test_append_parameter to use in_line writes.
Changes assertion method.
Adds assertion for duplicate parameter.
Use 1.x bootstrap only
Merge pull request #45 from oceanzus/append_param

Append parameter
Adds new submodule extern/ion-functions
Merge pull request #50 from lukecampbell/ion_functions

Adds new submodule extern/ion-functions
Bumps all submodules to latest
Merge pull request #51 from blazetopher/submod_bumps

Bumps all submodules to latest
Adds new files supporting the refactored nosetests framework.
Adds time axis to 'time' parameter.