Manta

- Rework the packaging for `pip install manta` et al to work.
Drop siloed 3rd party deps. This work inspired and mostly
copied from [deserat's](https://github.com/deserat) pull 10.

- [issue 12] Fixes for `MantaClient.put_object`.

- [issue 9, MANTA-1593] Proper URI encoding (RFC3986).

- [MANTA-1478] Properly handle paging through ListDirectory results. Before
this, `<MantaClient>.ls(...)` and `mantash ls` would not return all
entries in a directory with greater than ~256 entries.

- Add 'mantash open MANTA-PATH' to open a file in Manta in your browser.

- Rename 'mantash gzcat ...' to 'mantash zcat ...' as it should have been.

- [issue 8] A start at Python 3 support. This is **incomplete**. Paramiko
doesn't support Python 3 so we are stuck. Update to httplib2 0.8.

- Fix parsing of DSA pubkeys when generating a pubkey fingerprint
for `MANTA_KEY_ID=<path to ssh private key>` usage.

- [MANTA-1299] Backward incompatible change. Update to the new http-signature
signing scheme. <http://tools.ietf.org/html/draft-cavage-http-signatures-00>

- Backward incompatible change. Update `manta.MantaClient` "user" field to
"account" and `mantash` top-level options to mimic (as much as possible)
the [node-manta](https://github.com/joyent/node-manta)
CLI tools (e.g. `mls -h`).