If there is no server_version in the config file, automatically add it

when generating the new config file (#229).  However, don't add it if it
was already present in the config file, or if the config file already
exists (in which case, the appropriate action is to use the version
given, or back up the old config file).

blockstack/lib/config.py

@@ -23,6 +23,7 @@
 
 import os
 import sys
+import copy
 from ConfigParser import SafeConfigParser
 import pybitcoin
 import blockstack_utxo
@@ -494,9 +495,9 @@ def default_blockstack_opts( config_file=None ):
    serve_profiles = False
    zonefile_dir = None
    analytics_key = None
-   zonefile_storage_drivers = ""
+   zonefile_storage_drivers = "disk"
    profile_storage_drivers = ""
-   server_version = ""
+   server_version = None
 
    if parser.has_section('blockstack'):
 
@@ -702,7 +703,18 @@ def configure( config_file=None, force=False, interactive=True ):
    # if we prompted, then save
    if num_bitcoind_prompted > 0 or num_blockstack_opts_prompted > 0:
        print >> sys.stderr, "Saving configuration to %s" % config_file
-       blockstack_client.config.write_config_file( ret, config_file )
+   
+       # always set version when writing
+       config_opts = copy.deepcopy(ret)
+       if not config_opts['blockstack'].has_key('server_version'):
+           config_opts['blockstack']['server_version'] = VERSION
+
+       # if the config file doesn't exist, then set the version 
+       # in ret as well, since it's what's written
+       if not os.path.exists(config_file):
+           ret['blockstack']['server_version'] = VERSION
+
+       blockstack_client.config.write_config_file( config_opts, config_file )
 
    # prefix our bitcoind options, so they work with virtualchain
    ret['bitcoind'] = blockstack_client.config.opt_restore("bitcoind_", ret['bitcoind'])