Update dependencies in Cargo.toml + build instructions

I was able to get the blinky example to build and run on a
SAML11 Xplained board with these changes.

Looks like you were able to upstream the `thumbv8m.base-none-eabi`
target definition:

rust-lang/rust#55041

I was able to use that via rustup on a recent nightly, so no more need
for (patched) xargo.

I went ahead and bumped all of the crates to the latest releases as I
wasn't able to get anything to compile without doing so.

All that said, I was able to blink an LED on a SAML11 Xplained.

Cargo.toml

@@ -6,31 +6,23 @@ version = "0.1.0"
 [dependencies]
 bare-metal = "0.2.0"
 vcell = "0.1.0"
-
-[dependencies.cortex-m]
-git = "https://github.com/rust-embedded/cortex-m"
-rev = "b70a2179f4e8ee7908b61a6a97970e0cfcf2f313"
-
-[dependencies.cortex-m-rt]
-git = "https://github.com/rust-embedded/cortex-m-rt"
-rev = "9cd01176a6a9985c9bc0040801ed593687dd6ab1"
-optional = true
-
-[dev-dependencies.cortex-m-rt]
-git = "https://github.com/rust-embedded/cortex-m-rt"
-rev = "9cd01176a6a9985c9bc0040801ed593687dd6ab1"
-
-[dev-dependencies.cortex-m-semihosting]
-git = "https://github.com/rust-embedded/cortex-m-semihosting"
-rev = "471378bc848172e12e22b9a3b83190747e70bf5c"
-
-[dev-dependencies.panic-semihosting]
-git = "https://github.com/evq/panic-semihosting"
-rev = "3d7041af24969f32606e5eb804e23eaac7fb0bfa"
+cortex-m = "0.6"
+cortex-m-rt = { version = "0.6", optional = true }
+cortex-m-semihosting = "0.3"
+panic-semihosting = "0.5"
 
 [features]
+default = ["rt"]
 rt = ["cortex-m-rt/device"]
 
 [profile.release]
 debug = false
 lto = true
+
+[[example]]
+name = "blink"
+required-features = ["rt"]
+
+[[example]]
+name = "hello"
+required-features = ["rt"]

README.md

@@ -6,18 +6,22 @@ Peripheral access API for SAM L11 microcontrollers
 
 # WIP
 
-This crate is a work in progress. Building it either requires
-a xargo change or renaming the target spec due to the target
-naming convention used.
-
-https://github.com/japaric/xargo/pull/226
+This crate is a work in progress.
 
 ## Usage
 
 ### Building the blink example
 
+You'll need a recent Rust `nightly` build. Add the `thumbv8m.base-none-eabi` target:
+
+```
+$ rustup target add thumbv8m.base-none-eabi
+```
+
+Then use cargo to build the example:
+
 ```
-RUST_TARGET_PATH=`pwd` xargo build --release --target thumbv8m.base-none-eabi --example blink
+$ cargo build --release --example blink
 ```
 
 ### Programming blink example to FLASH on the SAM L11 XPLAINED dev board