use CRAN release of vegawidget (#124)

* bump version

* update to Vega 4.0.0

* update S3 methods to use altair v4 (vs v3)

patch gallery so examples work using v4

* Point remote to vegawidget master-branch

* update to new CRAN release of vegawidget

* roxygenize

* remove empty line

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: altair
-Version: 4.0.0.9000
+Version: 4.0.0.9001
 Title: Interface to 'Altair'
 Description: Interface to 'Altair' <https://altair-viz.github.io>, which itself 
   is a 'Python' interface to 'Vega-Lite' <https://vega.github.io/vega-lite>.
@@ -41,7 +41,7 @@ Imports:
     magrittr,
     jsonlite,
     utils,
-    vegawidget (>= 0.2.2.9000),
+    vegawidget (>= 0.3.1),
     repr
 Suggests:
     httr,
@@ -63,6 +63,4 @@ Suggests:
     png,
     fs
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 6.1.1
-Remotes: 
-  vegawidget/vegawidget
+RoxygenNote: 7.0.2

README.md

@@ -86,7 +86,7 @@ to convert Altair charts into SVG strings or write SVG files. With the
 **[png](https://CRAN.R-project.org/package=png)** packages installed,
 you can get a bitmap array, or write PNG files.
 
-When knitting to a non-HTML format, e.g. `github_document`, this package
+When knitting to a non-HTML format, e.g. `github_document`, this package
 provides a `knit_print()` function that will intercept the normal
 renderer, using instead its own renderer, allowing you to specify
 `"png"` , `"svg"` or `"pdf"`. Like the image functions, this requires
@@ -122,9 +122,9 @@ Some things to keep in mind:
   - Where you see a `.` in the Python examples, use a `$` instead.
 
   - In your data, columns that contain dots can be wrapped in square
-    brackets in Altair specifications, e.g. `[Sepal.Width]`, to keep
+    brackets in Altair specifications, e.g. `[Sepal.Width]`, to keep
     Altair from throwing an error. Alternatively, you can use a
-    double-backslash, e.g. `Sepal\\.Width`.
+    double-backslash, e.g. `Sepal\\.Width`.
 
 These and other “gotchas” are compiled, along with workarounds, in an
 article: [Field Guide to Python
@@ -137,8 +137,7 @@ The documentation for this package includes some
 
   - [Getting
     Started](https://vegawidget.github.io/altair/articles/altair.html):
-    a walkthrough to get a first chart to
-    work
+    a walkthrough to get a first chart to work
 
   - [Installation](https://vegawidget.github.io/altair/articles/installation.html):
     some more-detailed instructions