Added cbind functions and tests
Added rbind functions and tests
Extra test to cbind and rbind
cbind: functions with correct promotion of args and added agrad-rev tests
rbind: functions with correct promotion of args and added agrad-rev tests
Some basic fwd-rev tests for cbind and rbind
Added cbind and rbind to function signatures and related signature tests
Minor improments to rbind and cbind
Fix incorrect reference to inverse in to_matrix function signature test
Added documentation for cbind and rbind + minor fix for Transposition Postfix Operator documentation
Fixed typo in rbind documentation as was pointed out by Peter Li
Merge branch 'develop' into feature/issue-787-cbind-rbind
Renamed cbind and rbind to append_col and append_row, respectively
Fix wrong test names
Merge branch 'develop' into feature/issue-787-cbind-rbind
added append_row and append_col to parser_tests
Merge pull request #790 from stan-dev/feature/issue-787-cbind-rbind

Feature: functions cbind and rbind (fix issue 787)