Feature/memo rust

[whatisinternet]

What it does:

• Swaps inflections for inflector to increase performance
• Adds memoization option for rust wrapped in ruby
• Fixes up minor issues with README

  Why it does it:

• Inflector is fast now 😄
• Closes #4
• README was out of date and missing important information

[NullVoxPopuli]

I'm transitioning this project to helix at the moment. But this work won't be forgotten! It's very valuable if people can afford the memory tradeoff.