## Bug description

We've had a user create a funnel with Korean characters and 17 steps, which causes this issue:
![image](https://user-images.githubusercontent.com/1727427/120301818-8c212a00-c2cd-11eb-8b00-7ba242e4a9ab.png)

## Expected behavior

We should send requests to api/insight/funnel using POST instead of GET.

## How to reproduce

1.
2.
3.

## Environment

- [ ] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: _please provide_

## Additional context



#### *Thank you* for your bug report – we love squashing them!

posthog/utils.py
"""
    Decodes base64 bytes into string taking into account necessary transformations to match client libraries.
    """
    if not isinstance(data, str):
        data = data.decode()
    data = base64.b64decode(data.replace(" ", "+") + "===")
    return data.decode("utf8", "surrogatepass").encode("utf-16", "surrogatepass")
def load_data_from_request(request):
    data = None
    if request.method == "POST":
        if request.content_type in ["", "text/plain", "application/json"]:
            data = request.body
        else:
            data = request.POST.get("data")
    else:
        data = request.GET.get("data")
    if not data:
        return None
    
    with push_scope() as scope:
        scope.set_context("data", data)
    compression = (
        request.GET.get("compression") or request.POST.get("compression") or request.headers.get("content-encoding", "")
    )
    compression = compression.lower()