Clarify which Debian/Ubuntu flavour is needed for building

[bracki]

E.g. Wheezy doesn't work:

vagrant@jimdo-debian-7:~/apotiki$ cabal install
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: apotiki-0.5.2 (user goal)
next goal: base (dependency of apotiki-0.5.2)
rejecting: base-4.5.0.0/installed-40b... (conflict: apotiki => base>=4.6 &&
<4.7)
rejecting: base-4.6.0.1, 4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0,
4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0, 3.0.3.2, 3.0.3.1 (global
constraint requires installed instance)

[pyr]

Thanks, I'll spin up a wheezy

[bracki]

The released version doesn't work as well:

./apotiki: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.14' not found (required by ./apotiki)

[pyr]

indeed, it was tested on a recent ubuntu