Added automatic versioning

Based off the versioning in littlefs, which went through a number of
iterations before arriving at the current scheme

1. Version macros (EQUEUE_VERSION, EQUEUE_VERSION_MAJOR, and
   EQUEUE_VERSION_MINOR) are available in equeue.h for feature tests
2. These are used in CI to determine the current version
3. Additionally, CI keeps track of a simple incrementing patch number.
   Every time CI completes on master and is the most recent commit, a
   new patch number is generated, and a patch tag (ie v1.3.2) is
   created.
4. On top of this, CI will keep a major version branch (ie v1) updated
   to point to the most recent commit.
5. Each release, CI will automatically create release notes containing
   a list of new commits. This can be used as a starting point for
   additional notes and is a draft on major or minor releases.

Added workaround for armc assumptions on integer underflow

With ARM Compiler 5.06u3, when the equeue_tickdiff function is
inlined, the compiler treats the unsigned integer subtraction
as undefined behaviour and assumes falsely the comparisons
could never be true.

The workaround is to an explicit cast, which politely reminds the
compiler to emit the correct comparison.

Updated more documentation

- revisions to the README
- misspellings in equeue.h

Merge pull request #6 from geky/rename-equeue-calls

Rename event -> equeue for functions operating on queues

Updated README.md with information on tests/profiling

Fixed uncalled destructors on destruction of queue

Fixed cycle caused by incorrectly reregistering break event