title: install error for nmatrix gem in windows 8
body: <p>I am trying to install the nmatrix gem. i have the gcc compiler installed:</p>
  
  <pre><code>C:\dev\DNA&gt;gcc --version
  gcc (GCC) 4.9.3
  Copyright (C) 2015 Free Software Foundation, Inc.
  </code></pre>
  
  <p>then I have the following error on install:</p>
  
  <pre><code>C:\dev\DNA&gt;gem install nmatrix
  Temporarily enhancing PATH to include DevKit...
  Building native extensions.  This could take a while...
  ERROR:  Error installing nmatrix:
      ERROR: Failed to build gem native extension.
  
  C:/Ruby21/bin/ruby.exe extconf.rb
  using C++ standard... c++11
  g++ reports version... 4.7.2
  checking for rb_array_const_ptr() in ruby.h... no
  checking for FIX_CONST_VALUE_PTR in ruby.h... no
  checking for RARRAY_CONST_PTR in ruby.h... yes
  checking for RARRAY_AREF in ruby.h... yes
  creating nmatrix_config.h
  creating Makefile
  
  make "DESTDIR=" clean
  
  make "DESTDIR="
  generating nmatrix-i386-mingw32.def
  compiling nmatrix.cpp
  In file included from ./storage/storage.h:48:0,
               from util/io.h:38,
               from nmatrix.cpp:46:
  ./storage/common.h:155:3: error: 'u_int8_t' has not been declared
  ./storage/common.h:157:3: error: redefinition of 'VALUE       nm::ew_op_switch(LDType,
   RDType) [with nm::ewop_t op = (nm::ewop_t)3u; LDType = signed char; RDType    = in
  t; VALUE = long unsigned int]'
  ./storage/common.h:155:3: error: 'VALUE nm::ew_op_switch(LDType, RDType)    [with n
  m::ewop_t op = (nm::ewop_t)3u; LDType = signed char; RDType = int; VALUE =   long
  unsigned int]' previously declared here
  ./storage/common.h:165:3: error: 'u_int8_t' has not been declared
   ./storage/common.h:167:3: error: redefinition of 'VALUE    nm::ew_op_switch(LDType,
   RDType) [with nm::ewop_t op = (nm::ewop_t)3u; LDType = float; RDType = int;   VAL
   UE = long unsigned int]'
   ./storage/common.h:165:3: error: 'VALUE nm::ew_op_switch(LDType, RDType) [with n
   m::ewop_t op = (nm::ewop_t)3u; LDType = float; RDType = int; VALUE = long unsign
   ed int]' previously declared here
   ./storage/common.h:170:3: error: 'u_int8_t' has not been declared
   ./storage/common.h:172:3: error: redefinition of 'VALUE    nm::ew_op_switch(LDType,
   RDType) [with nm::ewop_t op = (nm::ewop_t)3u; LDType = double; RDType =   int; VA
   LUE = long unsigned int]'
   ./storage/common.h:170:3: error: 'VALUE nm::ew_op_switch(LDType, RDType) [with n
  m::ewop_t op = (nm::ewop_t)3u; LDType = double; RDType = int; VALUE = long   unsig
     ned int]' previously declared here
  In file included from nmatrix.cpp:283:0:
  ruby_nmatrix.c: In function 'VALUE nm_reshape_bang(VALUE, VALUE)':
  ruby_nmatrix.c:1102:11: warning: unused variable 'elem' [-Wunused-variable]
  ruby_nmatrix.c: In function 'VALUE nm_mset(int, VALUE*, VALUE)':
  ruby_nmatrix.c:2013:109: warning: format '%lu' expects argument of type 'long un
  signed int', but argument 4 has type 'size_t {aka unsigned int}' [-Wformat]
  ruby_nmatrix.c: In function 'VALUE nm_xslice(int, VALUE*, void* (*)(const   STORAG
  E*, SLICE*), void (*)(NMATRIX*), VALUE)':
  ruby_nmatrix.c:2251:92: warning: format '%lu' expects argument of type 'long uns
  igned int', but argument 4 has type 'size_t {aka unsigned int}' [-Wformat]
  ruby_nmatrix.c: In function 'SLICE* get_slice(size_t, int, VALUE*, size_t*)':
  ruby_nmatrix.c:2729:106: warning: format '%lu' expects argument of type 'long un
  signed int', but argument 3 has type 'size_t {aka unsigned int}' [-Wformat]
  ruby_nmatrix.c:2729:106: warning: format '%lu' expects argument of type 'long un
  signed int', but argument 4 has type 'size_t {aka unsigned int}' [-Wformat]
  ruby_nmatrix.c: In function 'void* interpret_initial_value(VALUE, nm::dtype_t)':
  
  ruby_nmatrix.c:2800:29: warning: comparison between signed and unsigned   integer
  expressions [-Wsign-compare]
  make: *** [nmatrix.o] Error 1
  
  make failed, exit code 2
  
  Gem files will remain installed in     C:/Ruby21/lib/ruby/gems/2.1.0/gems/nmatrix-0.
  2.1 for inspection.
  Results logged to C:/Ruby21/lib/ruby/gems/2.1.0/extensions/x86-mingw32/2.1.0/nma
  trix-0.2.1/gem_make.out
  </code></pre>
  
  <p>Would be really great to try out this library! Any ideas how to make the install succesful? thanks</p>