Updated docs in preparation for a release
Disabled IPv6 in an IPv4 database test.

I don't know what the intended behavior of the C library is. The
current and past behaviors are accidental.
Revert "Disabled IPv6 in an IPv4 database test."

This reverts commit 7302eaa2d92772011758b5f3bd3e4fe4a5bde481.
Return the correct exception for IPv6 lookup in IPv4 db
Tidied
Bumped version
gcc 4.4 doesn't work with -std=c99 flag
Only set -Werror for Travis
Prepare for 0.2.1
Working pure-Python reader.

All of the tests pass. On my machine, the reader does about 2000
lookups per second with CPython and about 7000 with PyPy.

I am still working on getting the conditional loading of the C
extension working. To do that, I need to make some changes to the
extension itself.
Allow graceful fallback to the pure Python module

Also brought the errors in line with the pure Python module.
Require ipaddr for older Pythons
Actually require the requirements
Test both the pure Python and extension in Travis
Increased compatibility between extension and PP implementation

For closed files. Also temporarily disabled a test. (Didn't use skip
as it isn't working on 2.6.)
Don't try to use python3 in Python 2 Travis instances
Update readme for module changes
Misc code cleanup and documentation
Run pylint from Travis
Minor cleanup