Fix "should-save" logic when deleting expired inbox message.
Add dev server identity file.

When running Pond with POND=dev, the default server is switched to
127.0.0.1 in order to help development. The public key for that
default, dev server is hardcoded in the client source and identity.dev,
in the server directory, is the private key needed for it.
Add a warning in documentation about using golang 1.0
custom tor address via env variable (closes #19)
Ignore invalid values of POND_TOR_ADDRESS.
Remove superfluous line break.
Merge branch 'kargig-fixdoc'