Build and import prefix data by chunks

Memory usage conserved when bytecode compiling.
New chunked data files
Merge pull request #34 from path/chunked-prefixdata

Chunked prefixdata
Update locale.py version number

Use the OS version on the main machine used for
development.
Bump version to 6.0.0a to avoid confusion
Warn that metadat loading might cause delay
Try building a phonenumbers-lite package variant
Don't use hyphen in package name
Use single setup.py for normal and lite packages

At package generation time, add a 'lite' command
line option that forces the light version of the
package.  At installation time, use absence of
phonenumbers/tzdata to indicate light version being
installed.

This is somewhat experimental; dynamically messing
with setup processing may well have unexpected side
effects.