context command does not handle context names with a '.' in them well

#### To report a bug...

Ran `task context define 'toolchain.taskwarrior' 'project:toolchain.taskwarrior'`
(with and without single quotes)

Expected new context `toolchain.taskwarrior` to be listed in context report: `task context list`
Got:

```
Name Type Definition Active
toolchain read no
write no
```

Notice that both the "Name" is wrong and "Definition" is blank.

Trying to delete the context with `task context delete toolchain`, throws an error:
`Context 'toolchain' not found.`

Yet, this works: `task context delete toolchain.taskwarrior`