Add support for parameters on inline partials/blocks

This adds support for passing parameters/attributes to inline partials/blocks. This change will cause inline partials to act almost exactly the same passing parameterss to a section or (non-inline) partial (wrt setting and passing parameters).

I've added tests for three use-cases, but am happy to add to or remove them if you think a different test would be more expressive of this change. Also, note, all tests are passing locally.

Below are a few more examples of how parameters on inline partials will work after this PR:
```
{! JSON: {"search_url": "http://google.com/search"} !}
{<partial}
Partial url is: {url}
{/partial}
{+partial url=search_url/}
```
Outputs: `Partial url is: http://google.com/search`

```
{<partial}
Partial url is: {url}
{/partial}
{+partial url="http://google.com/search"/}
```
Outputs: `Partial url is: http://google.com/search`

```
{! JSON: {"url": "http://google.com/search"} !}
{<partial}
Partial url is: {url}
{/partial}
{+partial/}
```
Outputs: `Partial url is: http://google.com/search`

```
{<partial}
Partial url is: {url}
{/partial}
{+partial url=nonExistentRef/}
```
Outputs: `Partial url is: `

```
{! JSON: {"search_url": { "value: "http://google.com/search" } } !}
{<partial}
Partial url is: {url.value}
{/partial}
{+partial url=search_url/}
```
Outputs: `Partial url is: http://google.com/search`

```
{! JSON: {"url": "http://google.com/search" } !}
{<partial}
Partial url is: {url}
{/partial}
{+partial url=search_url/}
```
Outputs: `Partial url is: http://google.com/search`

```
{! JSON: {"url": "http://google.com/search" } !}
{<partial}
Partial url is: {.url}
{/partial}
{+partial url=search_url/}
```
Outputs: `Partial url is:`

Thanks and let me know if I need to update any READMEs or wikis anywhere.