Localalias

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Fixed:

* Leaving a directory with local aliases should unmask globalaliases.

- Meaning that any global aliases that were previously overridden should be back in scope.

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Fixed:

* Local aliases were not consistently overriding global aliases

-------------------

Fixed:

* Local database was not being deleted consistently when empty, as it should be.

-------------------

Fixed:

* Add (``-a``) and Edit (``-e``) commands now act more approriately when command definition is left
blank.

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Changed:

* Local aliases are now sourced into ``.zshrc``.

Removed:

* Execute command (``-x``). No longer needed now that aliased are sourced directly into ``.zshrc``.
* Bash support

- I wanted to focus on providing one service well. ZSH has some more advanced features than bash.
Since I don't use bash, I'm not enthusiastic about supporting it. I'll reimplement it on
request, but am not going to waste my time otherwise.

-------------------

Fixed:

* Using ``-x`` without argument should fail explicitly. (v2.2.1 did not resolve this issue as I had
thought.)