Experimental release for all-Rust eBPF probes

This release adds experimental support for eBPF probes written completely in Rust.

Notably missing is thorough documentation at this stage, which will be added on the 0.9 branch as we stabilise 1.0.

Add aarch64/arm64 support

This is change is backwards compatible on x86_64, therefore this is just a maintenance release.
0.3.3 add support for building on arm64 on kernels <5.0.

Fix crash on single-core systems

The cpuid module now doesn't crash if the machine only has a single core in /sys/devices/system/cpu/online.

Fix bpf-sys versioning

No other changes from v0.3

Improve user experience

• Makes bpf-sys build against upstream libbpf
• Makes bpf-sys run bindgen from build.rs
• Support using kernel tree from $KERNEL_SOURCE or /lib/modules/$KERNEL_VERSION/build. $KERNEL_VERSION defaults to uname -r.
• Makes loading bpf programs work on Ubuntu/Debian by setting the correct kernel version as reported in /proc/version_signature.

Preventing bitrot

Update BCC/libbpf bindings
Update cargo dependencies
Add support for tracepoints
Better error handling

Updated crate documentation

v0.1.1

Update documentation to be hosted from redsift.github.io

Initial release

v0.1.0

Update Cargo.toml