Make use of the relative path when call the process.

[ftesser]

This PR Fix #32.

Trying to execute the command in the console without -interaction=batchmode pdflatex say that the file does not exist.
I noticed that in Windows 2016 the temp path of the latex file is composed by the compressed username "ADMINI~1" and not the real one "Administrator":

'['pdflatex', '-interaction=batchmode', '-halt-on-error', '-no-shell-escape', '-file-line-error', 'C:\\Users\\ADMINI~1\\AppData\\Local\\Temp\\3\\tmptebd6l1k\\tmptnlokmm8.latex']'

Using pdflatex in the console with "Administrator" instead of "ADMINI~1" the file is seen by pdflatex.
Probably the function that get the tempfiles in Windows 2016 is the real source of the problem here, but I have found another solution: make use of the relative path filename instead of the absolute one.

In fact the current directory of the commands is set to the temp directory and I do not see any contraindication to leave just the relative path (just the filename) starting from the tempdir:

['pdflatex', '-interaction=batchmode', '-halt-on-error', '-no-shell-escape', '-file-line-error', 'tmptnlokmm8.latex']

This solve my problem.