annoy

Essentially just #645 which fixes compilation on OS X

Fixed memory leak reported in #633

Add -fpermissive plus some other minor things

• Multithreaded building by @novoselrok
• Misc updates of README to link to Ruby bindings and clean up docs
• Better tree splitting, try multiple times ot find more balanced ones
• Fix building on disk and saving large files for Windows
• Misc compilation warnings cleanup

• mostly fixing windows issues with large files
• some error message improvements as well
• doing more stack allocations instead of heap
• fixes to a few tests that were failing on other platforms