Scalable comorbidities with sparse matrix multiplication

Version 3.0

• major improvement in comorbidity calculation speed using matrix multiplication behind the scenes. ICD-10 codes were slower than ICD-9 code comorbidities before, and are now 1.5 - 2 orders of magnitude faster.
• Added AHRQ clinical condition software (CCS) classification for ICD-9 and ICD-10, thanks to Vitaly Druker, fixes #127
• added 'charlson' synonyms for 'quan_deyo', e.g. Charlson comorbidities can now be found using comorbid_charlson(patient_data)
• Added AHRQ clinical condition software (CCS) classification for ICD-9 and ICD-10, thanks to Vitaly Druker, fixes #127
• function names have lost the 'icd_' prefix, old names kept for compatiblity, but easier now to write comorbid(patient_data), and icd::comorbid may also be used, and which many consider good practice.
• Assume C++11, which is now four years old, enabling code simplification
• rename all functions to remove the icd_, people can use the concise icd:: if library(icd) was not callled
• deprecated rarely or unused code, including %i9in%