The PQL looks like:
```
Range(frame=f, field0 >< [200,610])
```
One thing I noticed while implementing this is that it doesn't seem
like `FieldRange()` is used in either `Frame` or `View`; the Executor
calls `Fragment.FieldRange()` directly. The problem with this is that
the offset logic is calculated in the Frame, but since the Executor
doesn't go through Frame, then the Executor also has to calculate
the offset before calling `Fragment.FieldRange`. We should unify this
logic somewhere. Note, this applies to both `FieldRange` and
`FieldRangeBetween`.
This commit refactors the pilosa codebase. It makes several major
changes:
* Removes bitmap handles
* Removes dispatch/hold/transport
* Removes etcd dependency
* Adds consistent hash ring for slice placement
* Refactors parser/lexer
* Adds strong typing to PQL AST
* Flattens package hierarchy
