Add a script to measure memory use for building a 50_000 node tree

For reference, this was about 107.05MB on my machine when I first made the
script.
Add a new record type - ALIAS records

These are just like NODE records except that the iteration code will not
follow them when iterating over a tree.

This saves a little under 5mb when building & writing a 50,000 node tree.
Get stats before & after writing file to disk
Make sure to free all network structs we create
Add valgrind suppressions file

I copied this from MMDB XS reader since many of the core Perl suppressions would be the same
Make it possible to pass loops as a CLI argument
Make it possible to benchmark memory use with real data

Using this data shows that the vast majority of memory is used just created
the tree.
Make a few types in the node & record structs smaller

This doesn't seem to help memory usage, but it's a little more correct this
way, so it doesn't hurt to commit it.
Use uthash to manage the hash of record key -> data instead of Perl hashes & SVs

This lets us use char * keys which are _way_ smaller than the Perl SV * keys.

It's possible that this code is a little slower since we now have to SHA1-ify
each key to make it C-string safe (Sereal has \0 bytes). But on the plus side
running the keys through SHA1 makes them way smaller.
The key length is always the same (27) since we're using SHA1
Add some more Perl core suppressions
Check for uthash.h before trying to compile this code
Tidy Build.PL
Install uthash-dev as part of Travis build
Bump version in less memory branch
Ignore return value of hv_store()
Include version 1.9.7 of the uthash.h file in the repo

Ubuntu 10.04 has 1.8, which is missing the HASH_ITER macro.
Make sure to encode data into binary form before calling sha1_base64
Merge pull request #4 from maxmind/dave/use-less-memory

Reduce memory usage during writing