POST instead of GET for getTargetStates

[jrcain-usgs]

Fixes (for GetTargetStates at least) #113

Licensing

This project is mostly composed of free and unencumbered software released into the public domain, and we are unlikely to accept contributions that are not also released into the public domain. Somewhere near the top of each file should have these words:

This work is free and unencumbered software released into the public domain. In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain.

• I dedicate any and all copyright interest in this software to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

[chkim-usgs]

We only want to do a POST getTargetStates call if necessary. Doing a quick search, it looks like a safe URL character limit is 2000 so adding a URL character length check should do the trick. POST request if URL > 2000 characters, default can be a GET request.