This is the first pass on turning this plugin into a regular plugin,
instead of a ftplugin that only gets activated on Python files.
It also improves the behaviour, it's more robust now.

Seems robust enough.

The default Mint Vim is very old.

It's unnecessary, it sets the option right below.

This reverts commit 72be848.

By buffer-local and tab-local variables, by this order.

You can avoid creating the mappings with `g:pydoc_skip_mappings`
This is also the first step into breaking down the big plugin into more
manageable files.

And choose the appropriate pydoc. This is only useful on systems where
python2 and python3 coexist.
Can be skipped with the variable `let g:pydoc_detect_version = 0`

This changes several things:

- Introduce a new way algorithm for the `K` mapping, very useful to
  bring up help in many places.
- Organize the `ftplugin` folder in a more logical fashion.

This commit might look like a monster, but the algorithm change is the
more pressing matter.

This is useful for statusline purposes.

I reviewed most patterns for completeness and added a new heuristic that
"parses" the import lines for easier usage. When you use aliased
modules or functions in the code, it should be able to pickup what you
really meant.
It's still just regex trickery, it's not a real parser, so it might fail
on edge cases.
Should be pretty robust, here's some case it detects. `a`, `b` and `c`
can be submodules (having internal dots).

```python
from a import b as c
from a import b
import b as c
```

Thanks to @comeonfox for including a PR upstream that made me review
this.
#34

Fix python detection doesn't work when t:pydoc_cmd is defined.

If t:pydoc_cmd = 'pydoc' and b:pydoc_cmd = 'pydoc3' (like if you created
a new python file and then added a py3 shebang), then the old code would
use 'pydoc'. By grabbing the command before we switch buffers, we ensure
that we use the buffer-local value.

If user sets g:pydoc_cmd = 'python -m pydoc', then use that for the
detected pydoc command -- but with the appropriate version.

Fix 'press enter' prompt after :PyDoc commands.

Users don't need to know about these modifications and they're just
likely to require 'press enter' to proceed.

Test
:PyDoc dict.keys
:verbose PyDoc dict.keys
:PyDoc invalid

Update documentation to match their new names.

Names changed in 9f01eea.

Merge #3 #4

Merge #2