Adds troubleshooting info w.r.t. AbstractTrees

README.md

@@ -157,3 +157,17 @@ Currently for real-valued indices like time we are just rounding to the nearest
 ### Relative vs. Absolute indexing
 
 When we take a slice of a SampleBuf (e.g. take the span from 1s to 3s of a 10s audio buffer), what is the indexing domain of the result? Specifically, is it 1s-3s, or is it 0s-2s? For time-domain signals I can see wanting indexing relative to the beginning of the buffer, but in frequency-domain buffers it seems you usually want to keep the frequency information. Keeping track of the time information could also be useful if you split out a signal for processing and then want to re-combine things at the end.
+
+## AbstractTrees troubleshooting
+
+To run the SampledSignals tests you need Gumbo, but installing both Gumbo and Juno causes issues that prevent you from running the tests on 0.6. Here are the details:
+
+* AbstractTrees < v0.1.0 is not compatible with Julia v0.6
+* Gumbo 0.3.0 (latest) requires AbstractTrees >= v0.0.4
+* ASTInterpreter requires AbstractTrees between v0.0.4 and v0.1.0
+    * this limitation isn't in the REQUIRE in the repo, but was added to METADATA
+* ASTInterpreter is required by Atom and Gallium
+
+### Solution:
+
+Run `Pkg.checkout("ASTInterpreter")` and `Pkg.resolve()` until a new version is tagged. The ASTInterpreter tests don't pass, but it gets things working enough to get AbstractTrees back to 0.1.0 and the SampledSignals tests runnable.