Version 0.2: API rework, numpy bugfixes

(won't push version to 1.0 yet, remain in 0.* versioning scheme)

breaking

• Made all IO use BinaryIO objects from parameters, so the API is now IO independent
• Introduced a new File class, which offers more convenient access to data

enhancements

• exposed public API through __init__, so dependent projects don't have all that sub-module imports going on
• allow Neo versions >= 0.12, so the dependency doesn't break upgrade paths dependent projects
• Implemented more convenience functions for ChildContainer (see ChildContainer.path)

fixes

• Fixed NumPy string array allocation in Neo converter by @alinatroglio in #1