The generate-config command was printing a fixed string rather than calling
NewConfig() which is the canonical source for default config. I also noticed
that we were depending on two different toml libraries, and so collapsed that to
a single one. We have to use pelletier rather than BurntSushi because the viper
library that we use depends on pelletier.
these were occaisionally referenced elsewhere in the codebase - in all but one
case, there were workarounds that are actually better I think.
In the one case there wasn't I created a single top level DefaultConfig object
which is instantiated with all the default values and can be referred to if
necessary.
There was a bug in fragment.go with the way MaxWritesPerRequest was treated if
it was 0. Elsewhere, 0 meant no limit, but here, it would have caused a division
by 0.
Changed the default metrics provider from "nop" to "none", although "nop" will
still work. Previously, any value other than "statsd" or "expvar" was treated as
"nop", but I've changed this behavior to return an error if an invalid string is
provided. I think this is better behavior, because in the case that someone
bothered to change the default, they were probably interested in actually
getting stats, and might be annoyed when it silently failed.
