WIP: Implement writes series data on database

Not ready yet, just opening a PR to start some discussion.

The interface for interacting with the metastore feels clunky on my first pass trying to use it. I almost feel like there needs to be another abstraction over those transactions.

For example, this spot https://github.com/influxdb/influxdb/compare/write_series?expand=1#diff-320bbef96d874515320f176727a55ea8R410 where I have to close over the variables and set them feels really off.

Thoughts @benbjohnson?
A couple notes:

* You'll need to sort the keys first since the `map` is unordered.
* Since you'll have to iterate over the keys to build the key slice you might as well calculate the buffer size instead of using `bytes.Buffer`.
* You'll need to separate the keys & values with a delimiter since `{"foo":"bar","baz":"bat"}` will encode the same as `{"foob":"arb","azb":"at"}`. I usually just add a NULL byte (`\0`) after the key & value.
* If you are using `bytes.Buffer.Write()` you can skip the error check because it can't error: http://golang.org/src/pkg/bytes/buffer.go?s=4155:4206#L115