Fix FastComplex encoding when imaginary bits are negative
Fix encoding/decoding problems in FastComplex.

This expands on the work that Lukas Rytz did. There was
was another error (signed shift instead of unsigned),
and decoding code was simplified while remaining correct.
update authors file
Fix busted FastComplex test.

This really demonstrates the need to fix #286.
Bump scalaVersion to 2.11.2 in Build.scala

This commit finally gets Spire using 2.11 by default. The reason
we took so long getting here was all the warnings that our build
would spit out. This commit fixes all but 9 of the warnings.

Many warnings (unused imports, BigDecimal, etc) were dealt with
directly. However, there were a lot of deprecation warnings
involving macros where there was no obvious way to be compatible
with 2.10 but to ellide warnings in 2.11.

This commit solves the problem (well, mostly solves it) using
spire.macros.Compat, an object that contains methods implementing
the changed/deprecated methods (as well as a type alias for the
deprecated Context type). This means instead of hundreds of warnings
in the macros project, we now have 8, and we have 0 warnings
in core.

Sadly, there is still the persistent "Not a simple type" warning
as well.
Removed commented out code.

Thanks to @DRMacIver for keeping me honest.
bump travis version
Merge pull request #287 from non/topic/bump-to-211

Bump scalaVersion to 2.11.2 in Build.scala