Use strict mode when using moment.isValid to check date formatting.

[jwalgran]

Overview

Dates on the advanced search toolbar were being set incorrectly because the parsing a short date with the long date format was being interpreted as valid. Enabling "strict mode" makes the date parsing resolves this.

Connects #3245

Demo

Before

After

Testing

• Visit production https://www.opentreemap.org/phillytreemap/map/
• Open the advanced search menu, click on Tree Care, and select any values for the first 3 dropdowns
• Select May 1 in the date pickers and verify the bad behavior
• Repeat the process with a local instance and verify that setting May 1 in the date pickers works.

[coveralls]

Coverage remained the same at 83.867% when pulling 929595c31d84b37b013e288a76d010f9c3d49e8b on jcw/date-picker-bug into b7e7bbf474768511196862d92c496da34fc7d298 on develop.

[jwalgran]

@azavea-bot rebuild