add find methods to Series

- find in both ascending and descending order
- replace `firstValue` and `lastValue` with `findFirstValue` and `findLastValue`
Add Frame.fill constructor.
WIP: Blah.
Move sub-projects into root dir.

This gets rid of the modules sub-dir for sub-projects and just moves
them up to the root directory.
Merge pull request #18 from pellucidanalytics/topic/move-modules

Move sub-projects into root dir.
Add some more helper methods to Series.
Add new stats package with ops.

The only ops currently supported are `summary` on Frame and Series
types.
WIP: Add tests for summary.
Merge remote-tracking branch 'upstream/topic/frame-fill-construction' into topic/a-few-methods
Add summary spec.
Merge branch 'topic/generic-with-date' into topic/a-few-methods
Add reduceFrameWithCol method.
Add zipMap back to Cell.
Mean returns NA when there are only NAs.
Merge pull request #19 from pellucidanalytics/topic/a-few-methods

Add various methods to frame, series, cell, etc.
Merge remote-tracking branch 'dwhjames/topic/find-in-series'
Bump version to 0.1.1.
add denseValues method to Series

- method to access just the values of a series (ignoring non values if the series is sparse).
- add scaladoc for this and the `keys` and `values` methods
Merge pull request #21 from dwhjames/topic/denseValues

add denseValues method to Series