Add `snake_case`d function aliases in `__init__.py`

[TheGittyPerson]

The standard naming convention for Python function names is snake_case, as stated in Python's official style guide. Currently, the functions in __init__.py use lowerCamelCase (aka mixedCase):

def getHandler(access_token=None, **kwargs): ...
def getHandlerLite(access_token=None, **kwargs): ...
def getHandlerCore(access_token=None, **kwargs): ...
def getHandlerPlus(access_token=None, **kwargs): ...
def getHandlerAsync(access_token=None, **kwargs): ...
def getHandlerAsyncLite(access_token=None, **kwargs): ...
def getHandlerAsyncCore(access_token=None, **kwargs): ...
def getHandlerAsyncPlus(access_token=None, **kwargs): ...

Some code editors may highlight calls to these functions due to the styling issue, and styling-obsessed developers such as myself or teams who just prefer style consistency in their code would appreciate using the standard naming convention. Most other modules (specifically the ones whose names begin with handler) also have this issue, but we could just start with this one first.

With the concern of backwards compatibility, we can create aliases for these functions instead. The implementation should be fairly simple:

def get_handler(access_token=None, **kwargs):
    """Create and return Handler object."""
    return Handler(access_token, **kwargs)

def getHandler(access_token=None, **kwargs):
    """Create and return Handler object."""
    return Handler(access_token, **kwargs)
    # or:
    return get_handler(access_token, **kwargs)

Cons:

• Can be confusing to users who might think the different aliases have some different functionality.
  • Solution: we can note in the documentation that the functions and their aliases are equivalent.
• Namespace pollution
• I realized the problem was not only in __init__.py only after writing this issue.

I can open a PR for this if this change is ok. If there are other reasons that this change wouldn't be ideal, or if there is a better way to do this, please let me know.