Allow changes in vars to propagate

When injecting a var, do not deref, it so that changes are propagated.
This means the value of vars in the injected namespaces are themselves
vars rather than functions.  This should be transparent in most repl
usage.
Add Lazy injection of functions and macros

Eagerly loading all the namespaces of vars that you inject, can increase
your REPL start-up time, and increase the number of naamespaces that are
loaded in your REPL but not used in your projects.

This allows `:inject-ns-fns` and `:inject-ns-macros` to be used to
specify injections that will be loaded lazily.
Updated project.clj, release notes and readme for 0.2.0
Updated version for next release cycle