Fixed Auto-upgrade

[harinee]

The regex looking for the latest tag was looking for string 'Location', whereas the actual string is 'location'.
So, changed the regex to be case insensitive. Also, appended a semi-colon in the string to reduce the scope of search.
Fixes #221

[dcRUSTy]

https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.30
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Location
After looking at these two... the way Github has changed case of header name... I can predict next bug it will introduce is adding some random header along with location may be some thing like ****-Location or ***location which will require repatching this regex again... How about adding a ^ sign or something better in the regex? P.S. Not a expert in regex

[dineshba]

@harinee As @dcRUSTy suggested we can add ^location: when we do grep. As the response code for curl -I https://github.com/thoughtworks/talisman/releases/latest is 302 we will always get location in the response as per https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/302

And also it is good that we are doing -i while searching for location. Because http header field names are case-insensitive. https://stackoverflow.com/questions/5258977/are-http-headers-case-sensitive