Merge tag 'v0.5.1'

 * Fix GH-62: "empirical_frequencies" was not set when parsing PhyML AA statistics files.
Fix typo in README.rst
Do not use empirical frequencies for FastTree AA
Merge pull request #63 from fhcrc/63-fasttree-aa-emp-freqs-false

FastTree AA models should have `empirical_frequencies: false`
Bugfix: temporary files were not cleaned up.
CHANGELOG
Merge branch 'master' into dev