Failing to select version for cortex-m-rt

[Tacklebox]

I am trying to find a hello world/blinky project for getting started with the nRF52840-dk. When I follow the steps in the read me I get a linker error for the cortex-m-rt crate

cargo rb hello
    Updating crates.io index
error: failed to select a version for `cortex-m-rt`.
    ... required by package `nrf-hello-world v0.1.0 (/Users/me/Code/Embedded/nrf-hello-world)`
versions that meet the requirements `^0.7` are: 0.7.3, 0.7.0

the package `cortex-m-rt` links to the native library `cortex-m-rt`, but it conflicts with a previous package which links to `cortex-m-rt` as well:
package `cortex-m-rt v0.6.15`
    ... which satisfies dependency `cortex-m-rt = "^0.6.8"` of package `nrf52840-pac v0.9.0`
    ... which satisfies dependency `nrf52840-pac = "^0.9.0"` of package `nrf52840-hal v0.11.0`
    ... which satisfies dependency `nrf52840-hal = "^0.11.0"` of package `nrf-hello-world v0.1.0 (/Users/me/Code/Embedded/nrf-hello-world)`
Only one package in the dependency graph may specify the same links value. This helps ensure that only one copy of a native library is linked in the final binary. Try to adjust your dependencies so that only one package uses the `links = "cortex-m-rt"` value. For more information, see https://doc.rust-lang.org/cargo/reference/resolver.html#links.

failed to select a version for `cortex-m-rt` which could resolve this conflict