delete 'generated-sources' on each 'transpile' run

See #20, release log:

• 9e2b6f7 by @yegor256: #20 delete on start
• ce58f00 by @yegor256: #21 info log
• 67b3648 by @yegor256: #17 fix again
• 23c6d9f by @yegor256: #17 fixed itest
• 9562d6b by @yegor256: #17 show version

Released by Rultor 1.70.6, see build log