SeqOps maintains colletion types for ops.

This comes at the cost of specialization, due to some weird bug.
Clean-up of SeqOps required implicits.
Major additions/changes to spire.random.Generator &co.

This commit adds:

  * some new RNGs from Rex Kerr
  * (optional) synchronous generators
  * better support for seeds, initialization
  * gaussian wrapper to generate values in normal distributions
  * basic RNG benchmarks
  * basic RNG tests
  * other miscellaneous changes and fixes
uncomment and expand benchmarks; fix test
Add a brief RNG descriptiong
Merge remote-tracking branch 'tixxit/topic/seqops-ret-type' into 2.10.0
small typo, updated version
Merge pull request #77 from emchristiansen/2.10.0

small typo, updated version
Add cfor benchmarks that update an array.

This checkin adds a set of basic benchmarks that updates each element
in an array after multiplying the previous value by 2.

This benchmark was added to replicate an external spire benchmark in
which cfor seemed to be slower than while.  The benchmark results,
however, vary enough to be inconclusive at this point.  For example,
in the case where n = 1m (as in this benchmark), the 'while' case
on my machine varies between 3-4.5ms and the tailrec & cfor benchmarks
vary between 4-6 ms.
rename spire.random.Util to Pack
Move cfor to a while-loop instead of tailrec
Improve cfor's handling of non-literal function arguments.

This commit supports two styles of cfor:

1. "clean" where arguments are Function or Ident trees
(i.e. literal functions or references to previously-bound functions).

2. "dirty" where arguments must be rebound to vals
(e.g. for expressions return functions).

This fixes #75. Thanks to Olivier Chafik for catching this!
add some comments and clean up cfor
Fix cfor compiler crashes.

This commit improves the names that cfor uses, which were previously
causing a crash during later compiler phases.

Thanks to Olivier Chafik for spotting this!

Fixes #74.
Improve generated names as suggested by Olivier Chafik.
Fix Syntax.cforMacro#isClean (see non/spire#75)
make SafeLong constructor public
implement trig functions for Complex
give BigDecimal a faster sqrt method
Implement BigDecimal approximations of pi and e.

This is a work-in-progress. Currently we won't win any awards but at
least we'll be able to support the precisions that most people will
be intersted in.

We still need better precision for all the other methods in Trig but
at least this is a start.