v0.6.4

ModelBaseEcon v0.6.4

Diff since v0.6.3

Merged pull requests:

• Matrix parameters don't work (#69) (@bbejanov)
• Fix two problems with if-statements in equations (#71) (@bbejanov)
• Fix issues with equation parentheses (#72) (@Nic2020)
• eval_equation and tests (#74) (@Nic2020)
• Adding function checkmodel. (#75) (@bbejanov)

Closed issues:

• Matrix parameters don't work (#68)
• Two problems with using if statements in equations (#70)
• ModelBaseEcon.split_doc_tag_eqn() (#73)