MODIFIED, map_reads_to_reference supports choice of genetic_code

Modified the script with a --genetic_code option and modified the library
code to be aware of the option. Also changed the test code to include
the new option.
Merge branch 'map_reads_to_reference' of github.com:adamrp/qiime into map_reads_to_reference
modified NCBI web reference

URL is now more descriptive
Merge branch 'map_reads_to_reference' of github.com:adamrp/qiime into map_reads_to_reference
Merge branch 'master' of https://github.com/qiime/qiime into map_reads_to_reference
Fixing default value for params

Was set to {}, which can cause problems.
Changing imports to pull from pycogent_backports
Add app controllers to pycogent_backports

Controllers for BLAT and BWA, plus tests
Update link to NCBI URL, update changelog
Merge pull request #1264 from adamrp/map_reads_to_reference

Map reads to reference