Release: kompose binary should be statically linked

[janetkuo]

The latest release binary is dynamically linked. We should distribute statically linked binaries instead.

$ ldd kompose 
    linux-vdso.so.1 =>  (0x00007ffe937ea000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f0a7dae5000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0a7d720000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f0a7dd03000)

$ file kompose 
/usr/local/kompose: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=86c6d2ff21297a06cc7319244f35e2671612beae, not stripped

Setting CGO_ENABLED=0 should do the trick.

Ref #70