README update to note the 0.7 branch

README.md

@@ -7,6 +7,7 @@ One can still use it as a dependency directly from Git if desired, for example u
 ```
 implot = { git = "https://github.com/4bb4/implot-rs/", rev = "your_favourite_commit" }
 ```
+This is a work in progress. See the "Status" section below for notes on what is already built.
 
 ![demo](demo.png)
 
@@ -49,7 +50,11 @@ Once there are actual releases on crates.io, semantic versioning will be followe
 
 At this point, raw bindings are working in implot-sys, and more idiomatic interfaces
 for plot creation as well a subset of the functionality for plots are implemented. 
-See below for an overview of the progress.
+The master branch points to roughly implot 0.3, and a checklist of what is already
+implemented is shown below. Work is ongoing to move to implot 0.7 in the branch
+named `update-to-cimplot-0.7`. The latter branch is buildable, but work on wrapping
+the newly explicit contexts is not done yet, which is why it has not been merged into 
+master yet.
 
 - [x] "BeginPlot"
   - [x] Basic hello world