Breaking changes in 0.3

It looks like there's some breaking changes in 0.3. I haven't looked into them too fully yet but some of my tests are now breaking. Here's an example `FunctionClauseError` I'm getting.

```
** (FunctionClauseError) no function clause matching in Regex.replace/4

The following arguments were given to Regex.replace/4:

# 1
~r/['’]s/u

# 2
nil

# 3
"s"

# 4
[global: nil]

Attempted function clauses (showing 2 out of 2):

def replace(regex, string, replacement, options) when is_binary(string) and is_binary(replacement) and is_list(options)
def replace(regex, string, replacement, options) when is_binary(string) and is_function(replacement) and is_list(options)

code: conn = post conn, api_community_path(conn, :create), %{community: community_params}
stacktrace:
(elixir) lib/regex.ex:595: Regex.replace/4
(slugger) lib/slugger.ex:40: Slugger.slugify/2
```

Is there any documentation of the breaking changes?