Removing unnecessary functions for "detecting" context of the
class/function. Unifying regexp for detecting class/method/function,
get rid of excess iterator as a facade for vim buffer. Simplifying function
for gathering tags.

It seams, that entire block for looking for tags has been closed between
try:except keywords, catching all the exceptions, which is not necessary just
for iterating all over the file looking for particular pattern. Remove it
until real problem appear on wild - for sure I will extensively test that ;).

Provide alternative implementation of searching for the right tag.
Also, make functionality testable.

Otherwise it will point to the current path, instead of script path.
Changing it to script variables will change that behaviour to desirable one.

Move to python specific plugin (ftplugin),
Fixed bug regarding empty buffer.