Updating cortex-m crate dependency to v0.6+

[SaarYogev]

I encountered a bug (in the USART section of the embedded discovery book) where cortex_m::Peripherals::take().unwrap(); was hanging, around the Peripherals::steal() function.
Updating the cortex_m crate from version 0.5.6 to 0.6.3 solved the problem,
However, I did not find a sensible way to force-update the dependency in crates I depend upon such as this, leading to conflicts.

Can we update the dependency here so other people won't have this bug?

Also, as a workaround, is there a way to override the dependency version in packages, without downloading them locally? something like this:

cortex-m = "!0.6.3" #force updates to 0.6.3, regardless of what the package says.