Change docs references from "master" to "main" (#571)

CONTRIBUTING.md

@@ -33,7 +33,7 @@ Do you have an improvement?
 1. Submit an [issue][issue] describing your proposed change.
 2. We will try to respond to your issue promptly.
 3. Fork this repo, develop and test your code changes. See the project's [README](README.md) for further information about working in this repository.
-4. Submit a pull request against this repo's `master` branch.
+4. Submit a pull request against this repo's `main` branch.
 5. Your branch may be merged once all configured checks pass, including:
     - The branch has passed tests in CI.
     - A review from appropriate maintainers (see [MAINTAINERS.md](MAINTAINERS.md) and [GOVERNANCE.md](GOVERNANCE.md))
@@ -41,7 +41,7 @@ Do you have an improvement?
 ## Committing ##
 
 We prefer squash or rebase commits so that all changes from a branch are
-committed to master as a single commit. All pull requests are squashed when
+committed to `main` as a single commit. All pull requests are squashed when
 merged, but rebasing prior to merge gives you better control over the commit
 message.
 

profiling/README.md

@@ -102,12 +102,12 @@ different test runs. For example:
 
 ```console
 $ cd profiling/
-$ ./benchmark.sh ; git checkout master && ./benchmark.sh
+$ ./benchmark.sh ; git checkout main && ./benchmark.sh
 $ ./plot.sh \
     ../target/profile/2019Jun19_15h13m12s/summary.txt \
     ../target/profile/.2019Jun19_15h34m26s/summary.txt \
-    mybranch-vs-master-
-$ eog mybranch-vs-master-*png
+    mybranch-vs-main-
+$ eog mybranch-vs-main-*png
 ```
 
 Consider using `./plot.sh --logy ...` to switch the Y-axis to a logarithmic