Added ability to adjust for non-stationarity in TFCE-based methods. Still need to handle supra-threshold clustering
modified mrclusterstats to adjust of non-stationarity by default
mrclusterstats: added parameter comments in the output image headers
small fix to mrclusterstats
update non-stationary adjusment precomputation message
fixed bug n tfce nonstationary adjustment
Fixed some issues with tfce nonstationary adjustment
Added MR:File:exists() utility function
small update to tfce.h
removed exists() function from file utils
Minor stylistic changes
Major changes to handle thread-safe access to bitfields

Now use std::atomic functionality to allow thread-safe access to
bit-wise data, as per issue #98. **This means MRtrix now requires
the compiler to support C++11.** This is also relevant for issues #32
(move to C++11) and #31 (switch to non-GPL license).

The use of the std:atomic::compare_exchange_weak() function is also a
bit of a hack, relying on the implementation of std::atomic<T> being a
thin wrapper around its type T, with no additional state. This is the
case with GCC on Linux, and I expect any other compiler on relatively
recent Intel-compatible hardware. While this should cover the
overwhelming majority of likely MRtrix installations, there is a
distinct possibility that this will fail to compile or run on different
CPUs.

Will increment version number to duly reflect the ominousness of the
occasion...
BitSet: Use std::atomic

Similar modification to that used in put<bool> to ensure thread-safety
Tractography::Mapping::MapWriter: Fix maximum voxel-wise statistic

Use std::numeric_limits::lowest() to provide the smallest value available for the template type, regardless of floating-point / integer / signedness
Change all instances of isnan() and isinf() to std:: namespace

This was necessary for compilation with C++11 on my Windows machine, just as moving isfinite() to std:: was necessary in the past (for Macs from memory).
Fix header #define in tractography/mapping/mapper_plugins.h
dwi2fod: remove option to supply response coefficients directly on command-line

This is unnecessary and was causing issues - see issue #104 for details.
Closes #104.
configure: allow compilation under C++11 on MacOSX
Fixed seg fault in vector plot tool. Fixes #110
Removed unnecessary destructor in fixel class