CHOP-102. Scripts automatically import scalding and Express

issue: https://jira.kiji.org/browse/CHOP-102

Reviewed by: kiyan
Move some test dependencies to compile scope.

This commit modifies the pom to put kiji-schema's test jar and
fake-hbase into compile scope. This allows end-users to depend on the
KijiExpress testing framework and pick up these dependencies transitively.

Reviewed by: robertchu
CHOP-22. Design how users interact with Entity IDs

This includes all types of entity ids, including composite.

issue: https://jira.kiji.org/browse/CHOP-22
review: https://review.kiji.org/r/281/

reviewed by: kiyan, robert
CHOP-63. Add a series of descriptive stats methods to KijiSlice.

The following methods now exist on the KijiSlice class:
* min/max
* mean
* standard deviation
* variance
There are two versions of each method:
* One that requires a function argument that returns a numeric value in case the
  underlying KijiSlice cell is a complex Avro type.
* One that assumes the underlying KijiSlice cell value is numeric (a convenience
  version of the above. Code won't compile if the underlying cell type is not numeric).

Reviewed by: kiyan, robert
CHOP-63. Fix the max method which broke the build.
CHOP-71. Fix memoization of EntityIdFactory.

Reviewed by: kiyan