Error Check now happens only on text update, instead of running forever

When the text is modified in the textarea, only then update occurs. At other times, the error checker service thread stays idle.

P.S: This is my first time trying the pull request feature. I hope I'm doing this right. :p
P.P.S: I'm not sure how the older commits got added?! Also the "files changed", has some files which I hadn't changed myself?!