Fix Ruby regression with missing rb_complex_new function.

Affects Ruby versions prior to 1.9 using std::complex wrappers if just using std::complex
as an output type. Also fix the Complex helper functions external visibility (to static by default).

Closes #52
Remove lines with just spaces on them in Ruby docs
Remove use of monospace in Ruby docs and unncessary usage of <br>
Ruby html docs formatting - modify code snippets to be same as other chapters
Further Ruby html doc formatting changes