Remove some warnings

This commits remove below warnings on Ruby 1.9.3(MRI).

* ambiguous first argument; put parentheses or even spaces
* `*' interpreted as argument prefix
* instance variable @{ivar} not initialized

Note
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A warning is rest yet.

* character class has duplicated range

This fixes is https://github.com/kachick/leftright/commit/07a991d1eaff97323cf88dcae09f1029e5b11d44 .
But this is not correct, i guess.
I will pull-request other approaching in another issue.