Fix memoisation of lazy parser & bump version

Reported by @Rafiot: the lazy parser is not memoised, this has limited
effect on the basic / pure Python parser as its initialisation is
trivial, but it *significantly* impact the re2 and regex parsers as
they need to process regexes into a filter tree.

The memoization was mistakenly removed in #230: while refactoring
initialisation I removed the setting of the `parser` global.

- add a test to ensure the parser is correctly memoized, not
  re-instantiated every time
- reinstate setting the global
- add a mutex on `__getattr__`, it should only be used on first access
  and avoids two threads creating an expensive parser at the same
  time (which is a waste of CPU)

Fixes #253

Update version to 1.0

Hopefully I've not missed one hidden somewhere.

Also update the development status because y not.

Closes #234

Fix a bunch of URLs

- it's pypi.org not pypy.org
- rtfd doesn't serve docs out of its main domain (which makes sense
  since docs can contain arbitrary JS)
- add the doc and issues to the project URLs

Add doc badges, link action badge

Slightly late update of uap-core to 0.18.0

See ua-parser/uap-core@v0.16.0...v0.18.0
for the upstream changelog

Also remove 2.7 and 3.6 from the changelog as they're not accessible
from setup-python anymore, we'd need to e.g. install them by hand
using pyenv if we want to keep them (which might be a good idea but
it's not like anyone is touching the 0.x code so changes of breakage
are low anyway).

- actions/setup-python#672
- actions/setup-python#544

Release 0.16.1

Fixes concurrency issues with the cache invalidation mechanism.

Release 0.15.2

Fix for #132 on 0.15

Update uap-core to 0.16.0

Closes #129

Release 0.15.1

- removed version bound from `setup_requires`, allows building from
  source when only PyYaml 6.0 is available (and downloading 5.4 is
  not), #121, #125
- added type assertion to parser lookup, to make the error clearer on
  type error, #122, #123
- fixed `setup.py build_regexes` and `setup.py build` for non-in-place
  builds, #127

Deprecate js override bits

They were a feature for testing whose need was removed in
2015 (ua-parser/uap-core#58). They are *entirely* unnecessary, it is
possible a user somewhere is leveraging them for some reason.

So remove the override bits from the docstrings, and have them trigger
a `DeprecationWarning`.

Also:

- add tests that they do trigger
- remove support for them from the yaml testing functions
- update the pytest invocations to raise on all warnings
- while at it remove the apparently dead makePGTSComparisonYAML test
  utility method (?)
- and add pypy to the envlist

Note: `simplefilter` has to be updated to `"always"` for 2.7's dumb
      ass: the new tests triggers the same warning multiple times and
      of course `"default"` only yields them once.

Closes #119