Fixes failed build

On Debian 6.0 the build failed for me with following error:

```
make: Entering directory `/root/test/node-epeg/build'
  CXX(target) Release/obj.target/epeg/src/epeg.o
In file included from ../src/epeg.cc:4:
../src/Image.h:37: error: ISO C++ forbids initialization of member 'scaled'
../src/Image.h:37: error: making 'scaled' static
../src/Image.h:37: error: ISO C++ forbids in-class initialization of non-const static member 'scaled'
../src/Image.h:38: error: ISO C++ forbids initialization of member 'croped'
../src/Image.h:38: error: making 'croped' static
../src/Image.h:38: error: ISO C++ forbids in-class initialization of non-const static member 'croped'
make: *** [Release/obj.target/epeg/src/epeg.o] Error 1
```

gcc version:

```
gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.4.5-8' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --with-arch-32=i586 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.4.5 (Debian 4.4.5-8) 
```

When i initialize the variables scaled and croped in the constructor instead of in the header file the build works.

I'm not a C++ programmer, so i'm not sure about my fix... please check it well.