Updated integer regexp to allow for negatives

Found this while looking for TODOs

Implemented [this](http://stackoverflow.com/questions/16774064/regular-expression-for-whole-numbers-and-integers) pattern instead.  Added a unit test and it seems to be working.
    [+-]?
one of `+`, `-`, or nothing

    (?<!\.)
Negative lookbehind, makes sure that a literal dot will not be matched at this position

    \b
“the boundary between a word char (\w) and”

    [0-9]+
One or more digit

    \b
`-''-`

    (?!\.[0-9])
Negative lookahead, will make sure a literal dot followed by a digit is not matched

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All in all, it means that it will match things like `42`, `+42`, and `-42`, but not floats like `42.6` or `.42`