Fix mention of armrc in caveats

Placing your configuration in `~/.arm/.armrc` does not work.

The correct place to keep the configuration file is `~/.arm/armrc`, as can be seen here: https://github.com/flamsmark/arm/blob/e2e3091c1af2741e046831fdecd73677b3c1652b/src/starter.py#L35
arm: add 1.4.5.0 bottle.