Edit version string format

[shhyou]

raco pkg is not in favor of leading zeroes in the version string, as specified by valid-version?. Therefore, change 0.01 to 0.1. Fixes #50.

> (require version/utils)
> (valid-version? "0.01")
#f
> (valid-version? "0.1")
#t

Using 0.01 causes spurious raco setup errors:

raco setup: --- checking package dependencies ---                  [18:03:56]
raco setup: invalid package version declaration:
raco setup:   package: "pie"
raco setup:   declared version: "0.01"
raco setup: --- summary of package problems ---                    [18:04:01]
raco setup: package has invalid version:
raco setup:   package: "pie"
raco setup:   version: "0.01"
failed
 in build-one
 in loop
make: *** [in-place] Error 1

[shhyou]

@david-christiansen friendly ping