TODO

 [x] Nested Messages
 [x] Repeated
 [x] Repeated convenience methods (.add for pb, etc)
 [x] Better type validation
 [x] Nice __str__
 [x] Enum
 [x] Bool
 [x] Limit field numbers >= 1 and < 100k at higher levels (esp on set side)

 [x] Fixed fields
 [x] Double/float
 [x] Defaults
 [x] Comments
 [x] Imports
 [x] Enforce required
 [x] Clean up setup, palmc script, organize project, etc.
 [ ] Parent Chains (test parent chains, copy(), etc)

 [.] Heavy tests against google's official lib


Bugs/Incompletes
----------------

 * Not really honoring sfixed32 -- we write out as varint instead of min size 32
   (should probably use unsigned write as passthrough?)
 * Default without value not supported (type-implied default values)
 * Enum is not terribly crazy about enforcing the value is within range
 * No forward declarations..